Add Unit test

Author: schmidt-sebastian

firebase-firestore/src/test/java/com/google/firebase/firestore/local/LocalStoreTestCase.java

@@ -239,6 +239,31 @@ public void testHandlesSetMutationThenDocument() {
     assertContains(doc("foo/bar", 2, map("foo", "bar"), true));
   }
 
+  @Test
+  public void testHandlesSetMutationThenAckThenRelease() {
+    Query query = Query.atPath(ResourcePath.fromSegments(asList("foo")));
+    allocateQuery(query);
+
+    writeMutation(setMutation("foo/bar", map("foo", "bar")));
+    assertChanged(doc("foo/bar", 0, map("foo", "bar"), true));
+    assertContains(doc("foo/bar", 0, map("foo", "bar"), true));
+
+    acknowledgeMutation(1);
+    notifyLocalViewChanges(viewChanges(2, asList("foo/bar"), emptyList()));
+
+    assertChanged();
+    assertContains(doc("foo/bar", 0, map("foo", "bar"), true));
+
+    releaseQuery(query);
+
+    // It has been acknowledged, and should no longer be retained as there is no target and mutation
+    if (garbageCollectorIsEager()) {
+      assertNotContains("foo/bar");
+    } else {
+      assertContains(doc("foo/bar", 0, map("foo", "bar"), false));
+    }
+  }
+
   @Test
   public void testHandlesAckThenRejectThenRemoteEvent() {
     // Start a query that requires acks to be held.