diff --git a/src/test/java/com/googlesource/gerrit/plugins/zuul/GetCrdTest.java b/src/test/java/com/googlesource/gerrit/plugins/zuul/GetCrdTest.java
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index 0000000..019f5c3
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+++ b/src/test/java/com/googlesource/gerrit/plugins/zuul/GetCrdTest.java
@@ -0,0 +1,223 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.googlesource.gerrit.plugins.zuul;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.BranchNameKey;
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.entities.PatchSet;
+import com.google.gerrit.entities.Project;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.TopLevelResource;
+import com.google.gerrit.server.change.RevisionResource;
+import com.google.gerrit.server.restapi.change.ChangesCollection;
+import com.google.gerrit.server.restapi.change.QueryChanges;
+import java.sql.Timestamp;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+import org.eclipse.jgit.lib.ObjectId;
+import org.junit.Test;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+
+public class GetCrdTest {
+  private ChangesCollection changes;
+  private CommitMessageFetcher commitMessageFetcher;
+  private RevisionResource rsrc;
+
+  @Test
+  public void testNoDependencies() throws Exception {
+    String commitMessage = "subject";
+    configureMocks(commitMessage, new ArrayList<>());
+
+    GetCrd getCrd = createGetCrd();
+    Response<CrdInfo> response = getCrd.apply(rsrc);
+
+    assertThat(response.statusCode()).isEqualTo(200);
+    CrdInfo crdInfo = response.value();
+    assertThat(crdInfo.dependsOn).isEmpty();
+    assertThat(crdInfo.neededBy).isEmpty();
+    assertThat(crdInfo.cycle).isFalse();
+  }
+
+  @Test
+  public void testSingleDependsOn() throws Exception {
+    String commitMessage = "subject\nDepends-On: I00000000";
+    configureMocks(commitMessage, new ArrayList<>());
+
+    GetCrd getCrd = createGetCrd();
+    Response<CrdInfo> response = getCrd.apply(rsrc);
+
+    assertThat(response.statusCode()).isEqualTo(200);
+    CrdInfo crdInfo = response.value();
+    assertThat(crdInfo.dependsOn).containsExactly("I00000000");
+    assertThat(crdInfo.neededBy).isEmpty();
+    assertThat(crdInfo.cycle).isFalse();
+  }
+
+  @Test
+  public void testMultipleDependsOn() throws Exception {
+    String commitMessage =
+        "subject\nDepends-On: I00000000\nDepends-On: I00000002\nDepends-On: I00000004";
+    configureMocks(commitMessage, new ArrayList<>());
+
+    GetCrd getCrd = createGetCrd();
+    Response<CrdInfo> response = getCrd.apply(rsrc);
+
+    assertThat(response.statusCode()).isEqualTo(200);
+    CrdInfo crdInfo = response.value();
+    assertThat(crdInfo.dependsOn).containsExactly("I00000000", "I00000002", "I00000004");
+    assertThat(crdInfo.neededBy).isEmpty();
+    assertThat(crdInfo.cycle).isFalse();
+  }
+
+  @Test
+  public void testSingleNeededBy() throws Exception {
+    String commitMessage = "subject";
+    List<ChangeInfo> searchResults = new ArrayList<>();
+    searchResults.add(changeInfo("I00000001"));
+    configureMocks(commitMessage, searchResults);
+
+    GetCrd getCrd = createGetCrd();
+    Response<CrdInfo> response = getCrd.apply(rsrc);
+
+    assertThat(response.statusCode()).isEqualTo(200);
+    CrdInfo crdInfo = response.value();
+    assertThat(crdInfo.dependsOn).isEmpty();
+    assertThat(crdInfo.neededBy).containsExactly("I00000001");
+    assertThat(crdInfo.cycle).isFalse();
+  }
+
+  @Test
+  public void testMultipleNeededBy() throws Exception {
+    String commitMessage = "subject";
+    List<ChangeInfo> searchResults = new ArrayList<>();
+    searchResults.add(changeInfo("I00000001"));
+    searchResults.add(changeInfo("I00000003"));
+    searchResults.add(changeInfo("I00000005"));
+    configureMocks(commitMessage, searchResults);
+
+    GetCrd getCrd = createGetCrd();
+    Response<CrdInfo> response = getCrd.apply(rsrc);
+
+    assertThat(response.statusCode()).isEqualTo(200);
+    CrdInfo crdInfo = response.value();
+    assertThat(crdInfo.dependsOn).isEmpty();
+    assertThat(crdInfo.neededBy).containsExactly("I00000001", "I00000003", "I00000005");
+    assertThat(crdInfo.cycle).isFalse();
+  }
+
+  @Test
+  public void testMixed() throws Exception {
+    String commitMessage = "subject\nDepends-On: I00000002\nDepends-On: I00000004";
+    List<ChangeInfo> searchResults = new ArrayList<>();
+    searchResults.add(changeInfo("I00000001"));
+    searchResults.add(changeInfo("I00000003"));
+    configureMocks(commitMessage, searchResults);
+
+    GetCrd getCrd = createGetCrd();
+    Response<CrdInfo> response = getCrd.apply(rsrc);
+
+    assertThat(response.statusCode()).isEqualTo(200);
+    CrdInfo crdInfo = response.value();
+    assertThat(crdInfo.dependsOn).containsExactly("I00000002", "I00000004");
+    assertThat(crdInfo.neededBy).containsExactly("I00000001", "I00000003");
+    assertThat(crdInfo.cycle).isFalse();
+  }
+
+  @Test
+  public void testSimpleCycle() throws Exception {
+    String commitMessage = "subject\nDepends-On: I00000001";
+    List<ChangeInfo> searchResults = new ArrayList<>();
+    searchResults.add(changeInfo("I00000001"));
+    configureMocks(commitMessage, searchResults);
+
+    GetCrd getCrd = createGetCrd();
+    Response<CrdInfo> response = getCrd.apply(rsrc);
+
+    assertThat(response.statusCode()).isEqualTo(200);
+    CrdInfo crdInfo = response.value();
+    assertThat(crdInfo.dependsOn).containsExactly("I00000001");
+    assertThat(crdInfo.neededBy).containsExactly("I00000001");
+    assertThat(crdInfo.cycle).isTrue();
+  }
+
+  public void configureMocks(String commitMessage, final List<ChangeInfo> searchResult)
+      throws Exception {
+    String commitId = "0123456789012345678901234567890123456789";
+
+    Project.NameKey projectNameKey = Project.nameKey("projectFoo");
+
+    PatchSet patchSet = mock(PatchSet.class);
+    when(patchSet.commitId()).thenReturn(ObjectId.fromString(commitId));
+
+    Change change =
+        new Change(
+            Change.key("I0123456789"),
+            Change.id(4711),
+            Account.id(23),
+            BranchNameKey.create(projectNameKey, "branchBar"),
+            new Timestamp(0));
+
+    rsrc = mock(RevisionResource.class);
+    when(rsrc.getChange()).thenReturn(change);
+    when(rsrc.getPatchSet()).thenReturn(patchSet);
+
+    QueryChanges queryChanges = mock(QueryChanges.class);
+    final AtomicBoolean addedQuery = new AtomicBoolean(false);
+    doAnswer(
+            new Answer<Void>() {
+              @Override
+              public Void answer(InvocationOnMock invocation) throws Throwable {
+                addedQuery.getAndSet(true);
+                return null;
+              }
+            })
+        .when(queryChanges)
+        .addQuery("message:I0123456789 -change:I0123456789");
+    when(queryChanges.apply(TopLevelResource.INSTANCE))
+        .thenAnswer(
+            new Answer<Response<List<ChangeInfo>>>() {
+
+              @Override
+              public Response<List<ChangeInfo>> answer(InvocationOnMock invocation)
+                  throws Throwable {
+                return Response.ok(addedQuery.get() ? searchResult : null);
+              }
+            });
+
+    changes = mock(ChangesCollection.class);
+    when(changes.list()).thenReturn(queryChanges);
+
+    commitMessageFetcher = mock(CommitMessageFetcher.class);
+    when(commitMessageFetcher.fetch(projectNameKey, commitId)).thenReturn(commitMessage);
+  }
+
+  private ChangeInfo changeInfo(String changeId) {
+    ChangeInfo changeInfo = new ChangeInfo();
+    changeInfo.changeId = changeId;
+    return changeInfo;
+  }
+
+  private GetCrd createGetCrd() {
+    return new GetCrd(changes, commitMessageFetcher);
+  }
+}