diff --git a/src/main/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractor.java b/src/main/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractor.java
index 546e6c7..5ed4993 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractor.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractor.java
@@ -6,6 +6,7 @@
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gwtorm.server.OrmException;
+import com.google.inject.ImplementedBy;
 import com.google.inject.Inject;
 
 import com.googlesource.gerrit.plugins.its.base.its.ItsConfig;
@@ -24,13 +25,39 @@
       IssueExtractor.class);
 
   private final CommitMessageFetcher commitMessageFetcher;
-  private final ReviewDb db;
+  private final PatchSetDb db;
   private final ItsConfig itsConfig;
 
+  @ImplementedBy(PatchSetDbImpl.class)
+  public interface PatchSetDb {
+    public String getRevision(PatchSet.Id patchSetId);
+  }
+
+  public static class PatchSetDbImpl implements PatchSetDb {
+    private final ReviewDb db;
+
+    @Inject
+    public PatchSetDbImpl(ReviewDb db) {
+      this.db = db;
+    }
+
+    @Override
+    public String getRevision(PatchSet.Id patchSetId) {
+      try {
+        PatchSet previousPatchSet = db.patchSets().get(patchSetId);
+        if (previousPatchSet != null) {
+          return previousPatchSet.getRevision().get();
+        }
+      } catch (OrmException e) {
+        // previous is still empty to indicate that there was no previous
+        // accessible patch set. We treat every occurrence as added.
+      }
+      return null;
+    }
+  }
+
   @Inject
-  IssueExtractor(ItsConfig itsConfig,
-      CommitMessageFetcher commitMessageFetcher,
-      ReviewDb db) {
+  IssueExtractor(ItsConfig itsConfig, CommitMessageFetcher commitMessageFetcher, PatchSetDb db) {
     this.commitMessageFetcher = commitMessageFetcher;
     this.db = db;
     this.itsConfig = itsConfig;
@@ -188,23 +215,15 @@
    *    "subject". Issues in the last block get tagged with "footer". Issues
    *    occurring between "subject" and "footer" get tagged with "body".
    */
-  public Map<String,Set<String>> getIssueIds(String projectName,
-      String commitId, PatchSet.Id patchSetId) {
-    Map<String,Set<String>> current = getIssueIds(projectName, commitId);
+  public Map<String, Set<String>> getIssueIds(String projectName, String commitId, PatchSet.Id patchSetId) {
+    Map<String, Set<String>> current = getIssueIds(projectName, commitId);
     if (patchSetId != null) {
-      Map<String,Set<String>> previous = Maps.newHashMap();
+      Map<String, Set<String>> previous = Maps.newHashMap();
       if (patchSetId.get() != 1) {
-        PatchSet.Id previousPatchSetId = new PatchSet.Id(
-            patchSetId.getParentKey(), patchSetId.get() - 1);
-        try {
-          PatchSet previousPatchSet = db.patchSets().get(previousPatchSetId);
-          if (previousPatchSet != null) {
-            previous = getIssueIds(projectName,
-                previousPatchSet.getRevision().get());
-          }
-        } catch (OrmException e) {
-          // previous is still empty to indicate that there was no previous
-          // accessible patch set. We treat every occurrence as added.
+        PatchSet.Id previousPatchSetId = new PatchSet.Id(patchSetId.getParentKey(), patchSetId.get() - 1);
+        String previousPatchSet = db.getRevision(previousPatchSetId);
+        if (previousPatchSet != null) {
+          previous = getIssueIds(projectName, previousPatchSet);
         }
       }
 
diff --git a/src/test/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractorTest.java b/src/test/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractorTest.java
index b79e764..3e8721d 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractorTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractorTest.java
@@ -21,14 +21,13 @@
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.RevId;
-import com.google.gerrit.reviewdb.server.PatchSetAccess;
-import com.google.gerrit.reviewdb.server.ReviewDb;
-import com.google.gwtorm.server.OrmException;
+
 import com.google.inject.Guice;
 import com.google.inject.Injector;
 
 import com.googlesource.gerrit.plugins.its.base.its.ItsConfig;
 import com.googlesource.gerrit.plugins.its.base.testutil.LoggingMockingTestCase;
+import com.googlesource.gerrit.plugins.its.base.util.IssueExtractor.PatchSetDb;
 
 import org.junit.runner.RunWith;
 import org.powermock.core.classloader.annotations.PrepareForTest;
@@ -46,7 +45,7 @@
   private Injector injector;
   private ItsConfig itsConfig;
   private CommitMessageFetcher commitMessageFetcher;
-  private ReviewDb db;
+  private PatchSetDb db;
 
   public void testIssueIdsNullPattern() {
     IssueExtractor issueExtractor = injector.getInstance(IssueExtractor.class);
@@ -806,8 +805,7 @@
     assertLogMessageContains("Matching");
   }
 
-  public void testIssueIdsCommitWAddedSingleSubjectIssueSecondEmpty()
-      throws OrmException {
+  public void testIssueIdsCommitWAddedSingleSubjectIssueSecondEmpty() {
     expect(itsConfig.getIssuePattern()).andReturn(Pattern.compile("bug#(\\d+)"))
         .atLeastOnce();
     expect(itsConfig.getIssuePatternGroupIndex()).andReturn(1).atLeastOnce();
@@ -823,15 +821,7 @@
 
     // Call for previous patch set
     PatchSet.Id previousPatchSetId = new PatchSet.Id(changeId, 1);
-    RevId previousRevId = createMock(RevId.class);
-    expect(previousRevId.get())
-        .andReturn("9876543211987654321298765432139876543214").anyTimes();
-
-    PatchSet previousPatchSet = createMock(PatchSet.class);
-    expect(previousPatchSet.getRevision()).andReturn(previousRevId).anyTimes();
-
-    PatchSetAccess patchSetAccess = createMock(PatchSetAccess.class);
-    expect(patchSetAccess.get(previousPatchSetId)).andReturn(previousPatchSet);
+    expect(db.getRevision(previousPatchSetId)).andReturn("9876543211987654321298765432139876543214");
 
     expect(commitMessageFetcher.fetchGuarded("testProject",
         "9876543211987654321298765432139876543214")).andReturn(
@@ -839,8 +829,6 @@
             "\n" +
             "Change-Id: I9876543211987654321298765432139876543214");
 
-    expect(db.patchSets()).andReturn(patchSetAccess);
-
     PatchSet.Id currentPatchSetId = createMock(PatchSet.Id.class);
     expect(currentPatchSetId.get()).andReturn(2).anyTimes();
     expect(currentPatchSetId.getParentKey()).andReturn(changeId)
@@ -869,8 +857,7 @@
     assertLogMessageContains("Matching");
   }
 
-  public void testIssueIdsCommitWAddedSingleSubjectIssueSecondSame()
-      throws OrmException {
+  public void testIssueIdsCommitWAddedSingleSubjectIssueSecondSame() {
     expect(itsConfig.getIssuePattern()).andReturn(Pattern.compile("bug#(\\d+)"))
         .atLeastOnce();
     expect(itsConfig.getIssuePatternGroupIndex()).andReturn(1).atLeastOnce();
@@ -886,23 +873,13 @@
 
     // Call for previous patch set
     PatchSet.Id previousPatchSetId = new PatchSet.Id(changeId, 1);
-    RevId previousRevId = createMock(RevId.class);
-    expect(previousRevId.get())
-        .andReturn("9876543211987654321298765432139876543214").anyTimes();
-
-    PatchSet previousPatchSet = createMock(PatchSet.class);
-    expect(previousPatchSet.getRevision()).andReturn(previousRevId).anyTimes();
-
-    PatchSetAccess patchSetAccess = createMock(PatchSetAccess.class);
-    expect(patchSetAccess.get(previousPatchSetId)).andReturn(previousPatchSet);
-
     expect(commitMessageFetcher.fetchGuarded("testProject",
         "9876543211987654321298765432139876543214")).andReturn(
             "bug#42\n" +
             "\n" +
             "Change-Id: I9876543211987654321298765432139876543214");
 
-    expect(db.patchSets()).andReturn(patchSetAccess);
+    expect(db.getRevision(previousPatchSetId)).andReturn("9876543211987654321298765432139876543214");
 
     PatchSet.Id currentPatchSetId = createMock(PatchSet.Id.class);
     expect(currentPatchSetId.get()).andReturn(2).anyTimes();
@@ -931,8 +908,7 @@
     assertLogMessageContains("Matching");
   }
 
-  public void testIssueIdsCommitWAddedSingleSubjectIssueSecondBody()
-      throws OrmException {
+  public void testIssueIdsCommitWAddedSingleSubjectIssueSecondBody() {
     expect(itsConfig.getIssuePattern()).andReturn(Pattern.compile("bug#(\\d+)"))
         .atLeastOnce();
     expect(itsConfig.getIssuePatternGroupIndex()).andReturn(1).atLeastOnce();
@@ -948,16 +924,6 @@
 
     // Call for previous patch set
     PatchSet.Id previousPatchSetId = new PatchSet.Id(changeId, 1);
-    RevId previousRevId = createMock(RevId.class);
-    expect(previousRevId.get())
-        .andReturn("9876543211987654321298765432139876543214").anyTimes();
-
-    PatchSet previousPatchSet = createMock(PatchSet.class);
-    expect(previousPatchSet.getRevision()).andReturn(previousRevId).anyTimes();
-
-    PatchSetAccess patchSetAccess = createMock(PatchSetAccess.class);
-    expect(patchSetAccess.get(previousPatchSetId)).andReturn(previousPatchSet);
-
     expect(commitMessageFetcher.fetchGuarded("testProject",
         "9876543211987654321298765432139876543214")).andReturn(
             "subject\n" +
@@ -965,7 +931,7 @@
             "\n" +
             "Change-Id: I9876543211987654321298765432139876543214");
 
-    expect(db.patchSets()).andReturn(patchSetAccess);
+    expect(db.getRevision(previousPatchSetId)).andReturn("9876543211987654321298765432139876543214");
 
     PatchSet.Id currentPatchSetId = createMock(PatchSet.Id.class);
     expect(currentPatchSetId.get()).andReturn(2).anyTimes();
@@ -994,8 +960,7 @@
     assertLogMessageContains("Matching");
   }
 
-  public void testIssueIdsCommitWAddedSingleSubjectIssueSecondFooter()
-      throws OrmException {
+  public void testIssueIdsCommitWAddedSingleSubjectIssueSecondFooter() {
     expect(itsConfig.getIssuePattern()).andReturn(Pattern.compile("bug#(\\d+)"))
         .atLeastOnce();
     expect(itsConfig.getIssuePatternGroupIndex()).andReturn(1).atLeastOnce();
@@ -1012,23 +977,13 @@
 
     // Call for previous patch set
     PatchSet.Id previousPatchSetId = new PatchSet.Id(changeId, 1);
-    RevId previousRevId = createMock(RevId.class);
-    expect(previousRevId.get())
-        .andReturn("9876543211987654321298765432139876543214").anyTimes();
-
-    PatchSet previousPatchSet = createMock(PatchSet.class);
-    expect(previousPatchSet.getRevision()).andReturn(previousRevId).anyTimes();
-
-    PatchSetAccess patchSetAccess = createMock(PatchSetAccess.class);
-    expect(patchSetAccess.get(previousPatchSetId)).andReturn(previousPatchSet);
-
     expect(commitMessageFetcher.fetchGuarded("testProject",
         "9876543211987654321298765432139876543214")).andReturn(
             "bug#42\n" +
             "\n" +
             "Change-Id: I9876543211987654321298765432139876543214");
 
-    expect(db.patchSets()).andReturn(patchSetAccess);
+    expect(db.getRevision(previousPatchSetId)).andReturn("9876543211987654321298765432139876543214");
 
     PatchSet.Id currentPatchSetId = createMock(PatchSet.Id.class);
     expect(currentPatchSetId.get()).andReturn(2).anyTimes();
@@ -1059,8 +1014,7 @@
     assertLogMessageContains("Matching");
   }
 
-  public void testIssueIdsCommitWAddedSubjectFooter()
-      throws OrmException {
+  public void testIssueIdsCommitWAddedSubjectFooter() {
     expect(itsConfig.getIssuePattern()).andReturn(Pattern.compile("bug#(\\d+)"))
         .atLeastOnce();
     expect(itsConfig.getIssuePatternGroupIndex()).andReturn(1).atLeastOnce();
@@ -1079,16 +1033,6 @@
 
     // Call for previous patch set
     PatchSet.Id previousPatchSetId = new PatchSet.Id(changeId, 1);
-    RevId previousRevId = createMock(RevId.class);
-    expect(previousRevId.get())
-        .andReturn("9876543211987654321298765432139876543214").anyTimes();
-
-    PatchSet previousPatchSet = createMock(PatchSet.class);
-    expect(previousPatchSet.getRevision()).andReturn(previousRevId).anyTimes();
-
-    PatchSetAccess patchSetAccess = createMock(PatchSetAccess.class);
-    expect(patchSetAccess.get(previousPatchSetId)).andReturn(previousPatchSet);
-
     expect(commitMessageFetcher.fetchGuarded("testProject",
         "9876543211987654321298765432139876543214")).andReturn(
             "subject\n" +
@@ -1096,7 +1040,7 @@
             "\n" +
             "Change-Id: I9876543211987654321298765432139876543214");
 
-    expect(db.patchSets()).andReturn(patchSetAccess);
+    expect(db.getRevision(previousPatchSetId)).andReturn("9876543211987654321298765432139876543214");
 
     PatchSet.Id currentPatchSetId = createMock(PatchSet.Id.class);
     expect(currentPatchSetId.get()).andReturn(2).anyTimes();
@@ -1128,8 +1072,7 @@
     assertLogMessageContains("Matching");
   }
 
-  public void testIssueIdsCommitWAddedMultiple()
-      throws OrmException {
+  public void testIssueIdsCommitWAddedMultiple() {
     expect(itsConfig.getIssuePattern()).andReturn(Pattern.compile("bug#(\\d+)"))
         .atLeastOnce();
     expect(itsConfig.getIssuePatternGroupIndex()).andReturn(1).atLeastOnce();
@@ -1148,16 +1091,6 @@
 
     // Call for previous patch set
     PatchSet.Id previousPatchSetId = new PatchSet.Id(changeId, 1);
-    RevId previousRevId = createMock(RevId.class);
-    expect(previousRevId.get())
-        .andReturn("9876543211987654321298765432139876543214").anyTimes();
-
-    PatchSet previousPatchSet = createMock(PatchSet.class);
-    expect(previousPatchSet.getRevision()).andReturn(previousRevId).anyTimes();
-
-    PatchSetAccess patchSetAccess = createMock(PatchSetAccess.class);
-    expect(patchSetAccess.get(previousPatchSetId)).andReturn(previousPatchSet);
-
     expect(commitMessageFetcher.fetchGuarded("testProject",
         "9876543211987654321298765432139876543214")).andReturn(
             "subject\n" +
@@ -1166,7 +1099,7 @@
             "Bug: bug#16\n" +
             "Change-Id: I9876543211987654321298765432139876543214");
 
-    expect(db.patchSets()).andReturn(patchSetAccess);
+    expect(db.getRevision(previousPatchSetId)).andReturn("9876543211987654321298765432139876543214");
 
     PatchSet.Id currentPatchSetId = createMock(PatchSet.Id.class);
     expect(currentPatchSetId.get()).andReturn(2).anyTimes();
@@ -1216,8 +1149,8 @@
       commitMessageFetcher = createMock(CommitMessageFetcher.class);
       bind(CommitMessageFetcher.class).toInstance(commitMessageFetcher);
 
-      db = createMock(ReviewDb.class);
-      bind(ReviewDb.class).toInstance(db);
+      db = createMock(PatchSetDb.class);
+      bind(PatchSetDb.class).toInstance(db);
     }
   }
 }
\ No newline at end of file