diff --git a/java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java b/java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java
index c19358c..f03d337 100644
--- a/java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java
+++ b/java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java
@@ -43,7 +43,6 @@
 import org.eclipse.jgit.diff.RawTextComparator;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.ObjectId;
-import org.eclipse.jgit.lib.ObjectInserter;
 import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.merge.ThreeWayMergeStrategy;
@@ -167,12 +166,12 @@
       throws IOException {
     try (Timer0.Context ctx = codeOwnerMetrics.getAutoMerge.start();
         Repository repository = repoManager.openRepository(project);
-        ObjectInserter inserter = new InMemoryInserter(repository);
+        InMemoryInserter inserter = new InMemoryInserter(repository);
         ObjectReader reader = inserter.newReader();
         RevWalk revWalk = new RevWalk(reader)) {
       return autoMergerProvider
           .get()
-          .merge(repository, revWalk, inserter, mergeCommit, mergeStrategy);
+          .lookupFromGitOrMergeInMemory(repository, revWalk, inserter, mergeCommit, mergeStrategy);
     }
   }
 
diff --git a/java/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheck.java b/java/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheck.java
index 10d869b..b3a921e 100644
--- a/java/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheck.java
+++ b/java/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheck.java
@@ -174,37 +174,47 @@
     logger.atFine().log(
         "checking if change %d in project %s is submittable",
         changeNotes.getChangeId().get(), changeNotes.getProjectName());
-    boolean isSubmittable =
-        !getFileStatuses(changeNotes)
-            .anyMatch(
-                fileStatus ->
-                    (fileStatus.newPathStatus().isPresent()
-                            && fileStatus.newPathStatus().get().status()
-                                != CodeOwnerStatus.APPROVED)
-                        || (fileStatus.oldPathStatus().isPresent()
-                            && fileStatus.oldPathStatus().get().status()
-                                != CodeOwnerStatus.APPROVED));
-    logger.atFine().log(
-        "change %d in project %s %s submittable",
-        changeNotes.getChangeId().get(),
-        changeNotes.getProjectName(),
-        isSubmittable ? "is" : "is not");
-    return isSubmittable;
+    CodeOwnerConfigHierarchy codeOwnerConfigHierarchy = codeOwnerConfigHierarchyProvider.get();
+    try {
+      boolean isSubmittable =
+          !getFileStatuses(codeOwnerConfigHierarchy, changeNotes)
+              .anyMatch(
+                  fileStatus ->
+                      (fileStatus.newPathStatus().isPresent()
+                              && fileStatus.newPathStatus().get().status()
+                                  != CodeOwnerStatus.APPROVED)
+                          || (fileStatus.oldPathStatus().isPresent()
+                              && fileStatus.oldPathStatus().get().status()
+                                  != CodeOwnerStatus.APPROVED));
+      logger.atFine().log(
+          "change %d in project %s %s submittable",
+          changeNotes.getChangeId().get(),
+          changeNotes.getProjectName(),
+          isSubmittable ? "is" : "is not");
+      return isSubmittable;
+    } finally {
+      codeOwnerMetrics.codeOwnerConfigBackendReadsPerChange.record(
+          codeOwnerConfigHierarchy.getCodeOwnerConfigCounters().getBackendReadCount());
+      codeOwnerMetrics.codeOwnerConfigCacheReadsPerChange.record(
+          codeOwnerConfigHierarchy.getCodeOwnerConfigCounters().getCacheReadCount());
+    }
   }
 
   /**
    * Gets the code owner statuses for all files/paths that were changed in the current revision of
    * the given change as a set.
    *
-   * @see #getFileStatuses(ChangeNotes)
+   * @see #getFileStatuses(CodeOwnerConfigHierarchy, ChangeNotes)
    */
   public ImmutableSet<FileCodeOwnerStatus> getFileStatusesAsSet(ChangeNotes changeNotes)
       throws ResourceConflictException, IOException, PatchListNotAvailableException {
+    requireNonNull(changeNotes, "changeNotes");
     try (Timer0.Context ctx = codeOwnerMetrics.computeFileStatuses.start()) {
       logger.atFine().log(
           "compute file statuses (project = %s, change = %d)",
           changeNotes.getProjectName(), changeNotes.getChangeId().get());
-      return getFileStatuses(changeNotes).collect(toImmutableSet());
+      return getFileStatuses(codeOwnerConfigHierarchyProvider.get(), changeNotes)
+          .collect(toImmutableSet());
     }
   }
 
@@ -231,10 +241,13 @@
    *       approvals that were present on an old revision) would only confuse users
    * </ul>
    *
+   * @param codeOwnerConfigHierarchy {@link CodeOwnerConfigHierarchy} instance that should be used
+   *     to iterate over code owner config hierarchies
    * @param changeNotes the notes of the change for which the current code owner statuses should be
    *     returned
    */
-  public Stream<FileCodeOwnerStatus> getFileStatuses(ChangeNotes changeNotes)
+  private Stream<FileCodeOwnerStatus> getFileStatuses(
+      CodeOwnerConfigHierarchy codeOwnerConfigHierarchy, ChangeNotes changeNotes)
       throws ResourceConflictException, IOException, PatchListNotAvailableException {
     requireNonNull(changeNotes, "changeNotes");
     try (Timer0.Context ctx = codeOwnerMetrics.prepareFileStatusComputation.start()) {
@@ -307,31 +320,23 @@
 
       FallbackCodeOwners fallbackCodeOwners = codeOwnersConfig.getFallbackCodeOwners();
 
-      CodeOwnerConfigHierarchy codeOwnerConfigHierarchy = codeOwnerConfigHierarchyProvider.get();
-      try {
-        return changedFiles
-            .compute(changeNotes.getProjectName(), changeNotes.getCurrentPatchSet().commitId())
-            .stream()
-            .map(
-                changedFile ->
-                    getFileStatus(
-                        codeOwnerConfigHierarchy,
-                        branch,
-                        revision,
-                        globalCodeOwners,
-                        enableImplicitApprovalFromUploader,
-                        patchSetUploader,
-                        reviewerAccountIds,
-                        approverAccountIds,
-                        fallbackCodeOwners,
-                        hasOverride,
-                        changedFile));
-      } finally {
-        codeOwnerMetrics.codeOwnerConfigBackendReadsPerChange.record(
-            codeOwnerConfigHierarchy.getCodeOwnerConfigCounters().getBackendReadCount());
-        codeOwnerMetrics.codeOwnerConfigCacheReadsPerChange.record(
-            codeOwnerConfigHierarchy.getCodeOwnerConfigCounters().getCacheReadCount());
-      }
+      return changedFiles
+          .compute(changeNotes.getProjectName(), changeNotes.getCurrentPatchSet().commitId())
+          .stream()
+          .map(
+              changedFile ->
+                  getFileStatus(
+                      codeOwnerConfigHierarchy,
+                      branch,
+                      revision,
+                      globalCodeOwners,
+                      enableImplicitApprovalFromUploader,
+                      patchSetUploader,
+                      reviewerAccountIds,
+                      approverAccountIds,
+                      fallbackCodeOwners,
+                      hasOverride,
+                      changedFile));
     }
   }
 
diff --git a/java/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginConfigSnapshot.java b/java/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginConfigSnapshot.java
index 783019b..37b286b 100644
--- a/java/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginConfigSnapshot.java
+++ b/java/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginConfigSnapshot.java
@@ -19,6 +19,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableSetMultimap;
 import com.google.common.collect.Iterables;
 import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.common.Nullable;
@@ -34,10 +35,7 @@
 import com.google.gerrit.plugins.codeowners.backend.FallbackCodeOwners;
 import com.google.gerrit.plugins.codeowners.common.CodeOwnerConfigValidationPolicy;
 import com.google.gerrit.plugins.codeowners.common.MergeCommitStrategy;
-import com.google.gerrit.server.account.AccountResolver;
-import com.google.gerrit.server.account.AccountResolver.UnresolvableAccountException;
-import com.google.gerrit.server.account.AccountState;
-import com.google.gerrit.server.account.externalids.ExternalId;
+import com.google.gerrit.server.account.Emails;
 import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.gerrit.server.project.NoSuchProjectException;
 import com.google.gerrit.server.project.ProjectCache;
@@ -48,7 +46,6 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
-import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.lib.Config;
 
 /** Snapshot of the code-owners plugin configuration for one project. */
@@ -62,7 +59,7 @@
   private final String pluginName;
   private final PluginConfigFactory pluginConfigFactory;
   private final ProjectCache projectCache;
-  private final AccountResolver accountResolver;
+  private final Emails emails;
   private final BackendConfig backendConfig;
   private final GeneralConfig generalConfig;
   private final OverrideApprovalConfig overrideApprovalConfig;
@@ -78,7 +75,7 @@
       @PluginName String pluginName,
       PluginConfigFactory pluginConfigFactory,
       ProjectCache projectCache,
-      AccountResolver accountResolver,
+      Emails emails,
       BackendConfig backendConfig,
       GeneralConfig generalConfig,
       OverrideApprovalConfig overrideApprovalConfig,
@@ -88,7 +85,7 @@
     this.pluginName = pluginName;
     this.pluginConfigFactory = pluginConfigFactory;
     this.projectCache = projectCache;
-    this.accountResolver = accountResolver;
+    this.emails = emails;
     this.backendConfig = backendConfig;
     this.generalConfig = generalConfig;
     this.overrideApprovalConfig = overrideApprovalConfig;
@@ -225,36 +222,27 @@
   }
 
   private ImmutableSet<Account.Id> lookupExemptedAccounts() {
-    ImmutableSet.Builder<Account.Id> exemptedAccounts = ImmutableSet.builder();
-    for (String exemptedUser : generalConfig.getExemptedUsers(pluginConfig)) {
-      try {
-        AccountState accountState = accountResolver.resolve(exemptedUser).asUnique();
+    ImmutableSet<String> exemptedUsers = generalConfig.getExemptedUsers(pluginConfig);
 
-        // We only support specifying exempted users by email, if another account identifier (full
-        // name, account ID, etc.) was used in the config we want to ignore it. Hence after looking
-        // up the account we check that the identifier from the config was indeed an email of the
-        // account.
-        if (!ExternalId.getEmails(accountState.externalIds())
-            .anyMatch(email -> email.equals(exemptedUser))) {
-          logger.atWarning().log(
-              "Ignoring exempted user %s for project %s: not an email", exemptedUser, projectName);
-          continue;
-        }
+    try {
+      ImmutableSetMultimap<String, Account.Id> exemptedAccounts =
+          emails.getAccountsFor(exemptedUsers.toArray(new String[0]));
 
-        exemptedAccounts.add(accountState.account().id());
-      } catch (UnresolvableAccountException e) {
-        logger.atWarning().log(
-            "Ignoring exempted user %s for project %s: %s",
-            exemptedUser, projectName, e.getMessage());
-      } catch (IOException | ConfigInvalidException e) {
-        throw new CodeOwnersInternalServerErrorException(
-            String.format(
-                "Failed to resolve exempted user %s on project %s", exemptedUser, projectName),
-            e);
-      }
+      exemptedUsers.stream()
+          .filter(exemptedUser -> !exemptedAccounts.containsKey(exemptedUser))
+          .forEach(
+              exemptedUser ->
+                  logger.atWarning().log(
+                      "Ignoring exempted user %s for project %s: not found",
+                      exemptedUser, projectName));
+
+      return ImmutableSet.copyOf(exemptedAccounts.values());
+    } catch (IOException e) {
+      throw new CodeOwnersInternalServerErrorException(
+          String.format(
+              "Failed to resolve exempted users %s on project %s", exemptedUsers, projectName),
+          e);
     }
-
-    return exemptedAccounts.build();
   }
 
   /** Gets the override info URL that is configured. */
diff --git a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnerSubmitRuleIT.java b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnerSubmitRuleIT.java
index ecb1a9e..ef9c2b6 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnerSubmitRuleIT.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnerSubmitRuleIT.java
@@ -20,6 +20,8 @@
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
 
 import com.google.common.collect.ImmutableList;
+import com.google.gerrit.acceptance.PushOneCommit;
+import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.entities.BranchNameKey;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
@@ -297,4 +299,43 @@
         .hasMessageThat()
         .isEqualTo(String.format("destination branch \"refs/heads/%s\" not found.", branchName));
   }
+
+  @Test
+  @GerritConfig(name = "plugin.code-owners.exemptedUser", value = "exempted-user@example.com")
+  public void changeIsSubmittableIfUserIsExcempted() throws Exception {
+    TestAccount exemptedUser =
+        accountCreator.create(
+            "exemptedUser", "exempted-user@example.com", "Exempted User", /* displayName= */ null);
+
+    PushOneCommit.Result r = createChange(exemptedUser, "Some Change", "foo.txt", "some content");
+    String changeId = r.getChangeId();
+
+    // Apply Code-Review+2 by a non-code-owner to satisfy the MaxWithBlock function of the
+    // Code-Review label.
+    approve(changeId);
+
+    ChangeInfo changeInfo =
+        gApi.changes()
+            .id(changeId)
+            .get(
+                ListChangesOption.SUBMITTABLE,
+                ListChangesOption.ALL_REVISIONS,
+                ListChangesOption.CURRENT_ACTIONS);
+    assertThat(changeInfo.submittable).isTrue();
+
+    // Check that the submit button is enabled.
+    assertThat(changeInfo.revisions.get(r.getCommit().getName()).actions.get("submit").enabled)
+        .isTrue();
+
+    // Check the submit requirement.
+    SubmitRequirementInfoSubject submitRequirementInfoSubject =
+        assertThatCollection(changeInfo.requirements).onlyElement();
+    submitRequirementInfoSubject.hasStatusThat().isEqualTo("OK");
+    submitRequirementInfoSubject.hasFallbackTextThat().isEqualTo("Code Owners");
+    submitRequirementInfoSubject.hasTypeThat().isEqualTo("code-owners");
+
+    // Submit the change.
+    gApi.changes().id(changeId).current().submit();
+    assertThat(gApi.changes().id(changeId).get().status).isEqualTo(ChangeStatus.MERGED);
+  }
 }
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckTest.java
index d23f647..1023d2c 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckTest.java
@@ -14,17 +14,16 @@
 
 package com.google.gerrit.plugins.codeowners.backend;
 
-import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.allowLabel;
 import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThat;
 import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThatCollection;
-import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThatStream;
 import static com.google.gerrit.server.group.SystemGroupBackend.REGISTERED_USERS;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -45,7 +44,6 @@
 import com.google.inject.Inject;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.util.stream.Stream;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -78,7 +76,7 @@
     NullPointerException npe =
         assertThrows(
             NullPointerException.class,
-            () -> codeOwnerApprovalCheck.getFileStatuses(/* changeNotes= */ null));
+            () -> codeOwnerApprovalCheck.getFileStatusesAsSet(/* changeNotes= */ null));
     assertThat(npe).hasMessageThat().isEqualTo("changeNotes");
   }
 
@@ -97,10 +95,10 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -129,10 +127,10 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -158,10 +156,10 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().isEmpty();
     fileCodeOwnerStatusSubject.hasOldPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
@@ -188,8 +186,8 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    ImmutableList<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId)).collect(toImmutableList());
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     assertThatCollection(fileCodeOwnerStatuses).hasSize(2);
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject1 =
         assertThatCollection(fileCodeOwnerStatuses).element(0);
@@ -230,10 +228,10 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -264,10 +262,10 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -295,10 +293,10 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().isEmpty();
     fileCodeOwnerStatusSubject.hasOldPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
@@ -327,8 +325,8 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    ImmutableList<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId)).collect(toImmutableList());
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     assertThatCollection(fileCodeOwnerStatuses).hasSize(2);
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject1 =
         assertThatCollection(fileCodeOwnerStatuses).element(0);
@@ -369,8 +367,8 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    ImmutableList<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId)).collect(toImmutableList());
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     assertThatCollection(fileCodeOwnerStatuses).hasSize(2);
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject1 =
         assertThatCollection(fileCodeOwnerStatuses).element(0);
@@ -406,10 +404,10 @@
     requestScopeOperations.setApiUser(user.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -435,10 +433,10 @@
     requestScopeOperations.setApiUser(user.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -461,10 +459,10 @@
     requestScopeOperations.setApiUser(user.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().isEmpty();
     fileCodeOwnerStatusSubject.hasOldPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
@@ -489,8 +487,8 @@
     requestScopeOperations.setApiUser(user.id());
     recommend(changeId);
 
-    ImmutableList<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId)).collect(toImmutableList());
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     assertThatCollection(fileCodeOwnerStatuses).hasSize(2);
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject1 =
         assertThatCollection(fileCodeOwnerStatuses).element(0);
@@ -527,8 +525,8 @@
     requestScopeOperations.setApiUser(user.id());
     recommend(changeId);
 
-    ImmutableList<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId)).collect(toImmutableList());
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     assertThatCollection(fileCodeOwnerStatuses).hasSize(2);
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject1 =
         assertThatCollection(fileCodeOwnerStatuses).element(0);
@@ -574,10 +572,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
     amendChange(user, changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -617,10 +615,10 @@
             .getChangeId();
     amendChange(user, changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -656,10 +654,10 @@
     String changeId = createChangeWithFileDeletion(path);
     amendChange(user, changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().isEmpty();
     fileCodeOwnerStatusSubject.hasOldPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
@@ -698,8 +696,8 @@
     String changeId = createChangeWithFileRename(oldPath, newPath);
     amendChange(user, changeId);
 
-    ImmutableList<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId)).collect(toImmutableList());
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     assertThatCollection(fileCodeOwnerStatuses).hasSize(2);
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject1 =
         assertThatCollection(fileCodeOwnerStatuses).element(0);
@@ -750,8 +748,8 @@
     String changeId = createChangeWithFileRename(oldPath, newPath);
     amendChange(user, changeId);
 
-    ImmutableList<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId)).collect(toImmutableList());
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     assertThatCollection(fileCodeOwnerStatuses).hasSize(2);
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject1 =
         assertThatCollection(fileCodeOwnerStatuses).element(0);
@@ -788,10 +786,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
     amendChange(user, changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -817,10 +815,10 @@
     amendChange(user, changeId);
     amendChange(user2, changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -851,10 +849,10 @@
 
     // Verify that the file is not approved yet (the change owner is a code owner, but
     // implicit approvals are disabled).
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -867,8 +865,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -904,10 +902,10 @@
     String changeId =
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -937,10 +935,10 @@
 
     // Verify that the status of the file is INSUFFICIENT_REVIEWERS (since there is no implicit
     // approval by default).
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -952,8 +950,8 @@
     gApi.changes().id(changeId).addReviewer(user.email());
 
     // Check that the status of the file is PENDING now.
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -976,10 +974,10 @@
             .getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -998,8 +996,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1031,10 +1029,10 @@
         createChange(bot, "Change Adding A File", JgitPath.of(path).get(), "file content")
             .getChangeId();
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1060,10 +1058,10 @@
             .getChangeId();
 
     // Verify that the status of the file is INSUFFICIENT_REVIEWERS.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1076,8 +1074,8 @@
 
     // Check that the status of the file is PENDING now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1096,8 +1094,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1117,10 +1115,10 @@
 
     // Verify that the file is not approved yet (the change owner is a global code owner, but
     // implicit approvals are disabled).
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1133,8 +1131,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1165,10 +1163,10 @@
     String changeId =
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1190,10 +1188,10 @@
 
     // Verify that the status of the file is INSUFFICIENT_REVIEWERS (since there is no implicit
     // approval by default).
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1205,8 +1203,8 @@
     gApi.changes().id(changeId).addReviewer(user.email());
 
     // Check that the status of the file is PENDING now.
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1237,12 +1235,12 @@
     // Add code owner from a lower level as reviewer.
     gApi.changes().id(changeId).addReviewer(user2.email());
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     // The expected status is APPROVED since 'user' which is configured as code owner on the root
     // level approved the change.
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1271,9 +1269,7 @@
 
     // Without Owners-Override approval the expected status is INSUFFICIENT_REVIEWERS.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -1286,9 +1282,7 @@
 
     // With Owners-Override approval the expected status is APPROVED.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -1320,9 +1314,7 @@
 
     // Without override approval the expected status is INSUFFICIENT_REVIEWERS.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -1335,9 +1327,7 @@
 
     // With override approval the expected status is APPROVED.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -1350,9 +1340,7 @@
 
     // Without override approval the expected status is INSUFFICIENT_REVIEWERS.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -1365,9 +1353,7 @@
 
     // With override approval the expected status is APPROVED.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -1504,7 +1490,7 @@
     ResourceConflictException exception =
         assertThrows(
             ResourceConflictException.class,
-            () -> codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId)));
+            () -> codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId)));
     assertThat(exception).hasMessageThat().isEqualTo("destination branch not found");
   }
 
@@ -1522,10 +1508,10 @@
             .getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1544,8 +1530,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1569,8 +1555,8 @@
         .isEqualTo(user.email());
 
     // Check that the file is still approved.
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1596,10 +1582,10 @@
             .getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1612,8 +1598,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1636,8 +1622,8 @@
         .isEqualTo(admin.email());
 
     // Check that the file is still approved.
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1660,10 +1646,10 @@
             .getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1682,8 +1668,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1722,10 +1708,10 @@
             .getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1739,8 +1725,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1762,10 +1748,10 @@
             .getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1778,8 +1764,8 @@
     approve(changeId);
 
     // Verify that the file is not approved yet
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1798,8 +1784,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1821,10 +1807,10 @@
             .getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1843,8 +1829,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1873,10 +1859,10 @@
         createChange(user, "Change Adding A File", JgitPath.of(path).get(), "file content")
             .getChangeId();
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1901,10 +1887,10 @@
             .getChangeId();
 
     // Verify that the status of the file is INSUFFICIENT_REVIEWERS.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1917,8 +1903,8 @@
 
     // Check that the status of the file is PENDING now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1937,8 +1923,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -1961,10 +1947,10 @@
     String changeIdOfRevert = gApi.changes().id(changeId).revert().get().changeId;
 
     // Check that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeIdOfRevert));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeIdOfRevert));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasOldPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasOldPathStatus()
@@ -1988,10 +1974,10 @@
     String changeIdOfRevert = gApi.changes().id(changeId).revert().get().changeId;
 
     // Check that the file is approved since it's a pure revert.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeIdOfRevert));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeIdOfRevert));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasOldPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasOldPathStatus()
@@ -2025,10 +2011,10 @@
         "other content");
 
     // Check that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeIdOfRevert));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeIdOfRevert));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -2051,10 +2037,10 @@
 
     // Check that the file is approved since the uploader is exempted from requiring code owner
     // approvals.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -2068,8 +2054,8 @@
 
     // Check that the file is no longer approved since the uploader is not exempted from requiring
     // code owner approvals.
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithAllUsersAsFallbackCodeOwnersTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithAllUsersAsFallbackCodeOwnersTest.java
index 2807eb4..dc87ef7 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithAllUsersAsFallbackCodeOwnersTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithAllUsersAsFallbackCodeOwnersTest.java
@@ -14,8 +14,9 @@
 
 package com.google.gerrit.plugins.codeowners.backend;
 
-import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThatStream;
+import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThatCollection;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
@@ -31,7 +32,6 @@
 import com.google.inject.Inject;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.util.stream.Stream;
 import org.eclipse.jgit.lib.Config;
 import org.junit.Before;
 import org.junit.Test;
@@ -76,10 +76,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -92,8 +92,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -107,8 +107,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -130,10 +130,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -157,10 +157,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -173,8 +173,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -188,8 +188,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -215,10 +215,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -235,10 +235,10 @@
 
     // Verify that the file is not approved yet (the change owner is a code owner, but
     // implicit approvals are disabled).
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -250,8 +250,8 @@
     gApi.changes().id(changeId).addReviewer(user.email());
 
     // Verify that the status is pending now .
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -264,8 +264,8 @@
     recommend(changeId);
 
     // Verify that the status is approved now
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -283,10 +283,10 @@
 
     // Verify that the file is approved (the change owner is a code owner and implicit approvals are
     // enabled).
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -310,10 +310,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -326,8 +326,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -341,8 +341,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -367,10 +367,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -395,10 +395,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -411,8 +411,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -426,8 +426,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -453,10 +453,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -486,10 +486,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -502,8 +502,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -517,8 +517,8 @@
 
     // Verify that the file is not approved (fallback code owner doesn't apply since a code owner is
     // defined).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -550,10 +550,10 @@
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithProjectOwnersAsFallbackCodeOwnersTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithProjectOwnersAsFallbackCodeOwnersTest.java
index 15d0c51..3878a27 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithProjectOwnersAsFallbackCodeOwnersTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithProjectOwnersAsFallbackCodeOwnersTest.java
@@ -14,13 +14,13 @@
 
 package com.google.gerrit.plugins.codeowners.backend;
 
-import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.allowLabel;
 import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThat;
-import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThatStream;
+import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThatCollection;
 import static com.google.gerrit.server.group.SystemGroupBackend.REGISTERED_USERS;
 
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -37,7 +37,6 @@
 import com.google.inject.Inject;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.util.stream.Stream;
 import org.eclipse.jgit.internal.storage.dfs.InMemoryRepository;
 import org.eclipse.jgit.junit.TestRepository;
 import org.eclipse.jgit.lib.Config;
@@ -84,10 +83,10 @@
             .getChangeId();
 
     // Verify that the file is not approved yet.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -106,8 +105,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -139,10 +138,10 @@
         createChange(bot, "Change Adding A File", JgitPath.of(path).get(), "file content")
             .getChangeId();
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -168,10 +167,10 @@
             .getChangeId();
 
     // Verify that the status of the file is INSUFFICIENT_REVIEWERS.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -184,8 +183,8 @@
 
     // Check that the status of the file is PENDING now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -204,8 +203,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -225,10 +224,10 @@
 
     // Verify that the file is not approved yet (the change owner is a global code owner, but
     // implicit approvals are disabled).
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -241,8 +240,8 @@
 
     // Check that the file is approved now.
     requestScopeOperations.setApiUser(admin.id());
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -273,10 +272,10 @@
     String changeId =
         createChange("Change Adding A File", JgitPath.of(path).get(), "file content").getChangeId();
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -298,10 +297,10 @@
 
     // Verify that the status of the file is INSUFFICIENT_REVIEWERS (since there is no implicit
     // approval by default).
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -313,8 +312,8 @@
     gApi.changes().id(changeId).addReviewer(user.email());
 
     // Check that the status of the file is PENDING now.
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -342,10 +341,10 @@
     requestScopeOperations.setApiUser(user3.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -374,10 +373,10 @@
     requestScopeOperations.setApiUser(user2.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -401,10 +400,10 @@
     requestScopeOperations.setApiUser(admin.id());
     recommend(changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -438,10 +437,10 @@
     // Amend change with a user that is a project owner.
     amendChange(admin, changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -467,10 +466,10 @@
     // Amend change with a user that is not a project owner.
     amendChange(user, changeId);
 
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -503,9 +502,7 @@
 
     // Without Owners-Override approval the expected status is INSUFFICIENT_REVIEWERS.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -518,9 +515,7 @@
 
     // With Owners-Override approval the expected status is APPROVED.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -553,9 +548,7 @@
 
     // Without override approval the expected status is INSUFFICIENT_REVIEWERS.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -569,9 +562,7 @@
 
     // With override approval the expected status is APPROVED.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -584,9 +575,7 @@
 
     // Without override approval the expected status is INSUFFICIENT_REVIEWERS.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
@@ -599,9 +588,7 @@
 
     // With override approval the expected status is APPROVED.
     for (FileCodeOwnerStatus fileCodeOwnerStatus :
-        codeOwnerApprovalCheck
-            .getFileStatuses(getChangeNotes(changeId))
-            .collect(toImmutableList())) {
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId))) {
       assertThat(fileCodeOwnerStatus)
           .hasNewPathStatus()
           .value()
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithSelfApprovalsIgnoredTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithSelfApprovalsIgnoredTest.java
index 3112b07..a27bde9 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithSelfApprovalsIgnoredTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnerApprovalCheckWithSelfApprovalsIgnoredTest.java
@@ -14,8 +14,9 @@
 
 package com.google.gerrit.plugins.codeowners.backend;
 
-import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThatStream;
+import static com.google.gerrit.plugins.codeowners.testing.FileCodeOwnerStatusSubject.assertThatCollection;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
@@ -32,7 +33,6 @@
 import com.google.inject.Inject;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.util.stream.Stream;
 import org.eclipse.jgit.lib.Config;
 import org.junit.Before;
 import org.junit.Test;
@@ -83,10 +83,10 @@
             .getChangeId();
 
     // Verify that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -99,8 +99,8 @@
     recommend(changeId);
 
     // Verify that the file is not approved (since self approvals are ignored).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -125,10 +125,10 @@
     amendChange(admin, changeId);
 
     // Verify that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -142,8 +142,8 @@
 
     // Verify that the file is approved now (since the change owner is not the uploader of the
     // current patch set).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -172,10 +172,10 @@
     amendChange(codeOwner, changeId);
 
     // Verify that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -188,8 +188,8 @@
 
     // Verify that the file is not pending (the code owner is the uploader of the current patch set
     // and self approvals are ignored).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -203,8 +203,8 @@
 
     // Verify that the file is not approved (since the code owner is the uploader of the current
     // patch set and self approvals are ignored).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -227,10 +227,10 @@
             .getChangeId();
 
     // Verify that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -260,10 +260,10 @@
     amendChange(codeOwner, changeId);
 
     // Verify that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -286,10 +286,10 @@
             .getChangeId();
 
     // Verify that the file is approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -319,10 +319,10 @@
     amendChange(codeOwner, changeId);
 
     // Verify that the file is approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -343,10 +343,10 @@
             .getChangeId();
 
     // Verify that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -360,8 +360,8 @@
 
     // Verify that the file is not approved (since self approvals on the override label are
     // ignored).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -385,10 +385,10 @@
     amendChange(admin, changeId);
 
     // Verify that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -402,8 +402,8 @@
 
     // Verify that the file is approved now (since the change owner is not the uploader of the
     // current patch set and hence the override counts).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -427,10 +427,10 @@
     amendChange(admin, changeId);
 
     // Verify that the file is not approved.
-    Stream<FileCodeOwnerStatus> fileCodeOwnerStatuses =
-        codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
+    ImmutableSet<FileCodeOwnerStatus> fileCodeOwnerStatuses =
+        codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
     FileCodeOwnerStatusSubject fileCodeOwnerStatusSubject =
-        assertThatStream(fileCodeOwnerStatuses).onlyElement();
+        assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()
@@ -442,8 +442,8 @@
     gApi.changes().id(changeId).current().review(new ReviewInput().label("Owners-Override", 1));
 
     // Verify that the file is not approved (since the override from the uploader is ignored).
-    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatuses(getChangeNotes(changeId));
-    fileCodeOwnerStatusSubject = assertThatStream(fileCodeOwnerStatuses).onlyElement();
+    fileCodeOwnerStatuses = codeOwnerApprovalCheck.getFileStatusesAsSet(getChangeNotes(changeId));
+    fileCodeOwnerStatusSubject = assertThatCollection(fileCodeOwnerStatuses).onlyElement();
     fileCodeOwnerStatusSubject.hasNewPathStatus().value().hasPathThat().isEqualTo(path);
     fileCodeOwnerStatusSubject
         .hasNewPathStatus()