Test CreateMergePatchSet when there is a merge conflict

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: Ic39097d60264e6099bb8cbf22420fe2bcdf75d17

javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java

@@ -3199,6 +3199,41 @@ public class ChangeIT extends AbstractDaemonTest {
         .isEqualTo(parent);
   }
 
+  @Test
+  public void createMergePatchSet_Conflict() throws Exception {
+    RevCommit initialHead = projectOperations.project(project).getHead("master");
+    createBranch("dev");
+
+    // create a change for master
+    String changeId = createChange().getChangeId();
+
+    String fileName = "shared.txt";
+    testRepo.reset(initialHead);
+    PushOneCommit.Result currentMaster =
+        pushFactory
+            .create(admin.newIdent(), testRepo, "change 1", fileName, "content 1")
+            .to("refs/heads/master");
+    currentMaster.assertOkStatus();
+
+    // push a commit into dev branch
+    testRepo.reset(initialHead);
+    PushOneCommit.Result changeA =
+        pushFactory
+            .create(user.newIdent(), testRepo, "change 2", fileName, "content 2")
+            .to("refs/heads/dev");
+    changeA.assertOkStatus();
+    MergeInput mergeInput = new MergeInput();
+    mergeInput.source = "dev";
+    MergePatchSetInput in = new MergePatchSetInput();
+    in.merge = mergeInput;
+    in.subject = "update change by merge ps2";
+    ResourceConflictException thrown =
+        assertThrows(
+            ResourceConflictException.class,
+            () -> gApi.changes().id(changeId).createMergePatchSet(in));
+    assertThat(thrown).hasMessageThat().isEqualTo("merge conflict(s)\n" + fileName);
+  }
+
   @Test
   public void createMergePatchSetInheritParent() throws Exception {
     RevCommit initialHead = projectOperations.project(project).getHead("master");