Some cleanup in AabUpdaterTest (#3921)

Author: lfkellogg

firebase-appdistribution/src/test/java/com/google/firebase/appdistribution/impl/AabUpdaterTest.java

@@ -142,7 +142,7 @@ public void updateAppTask_emptyLocationHeader_setsDownloadFailure() throws Inter
 
   @Test
   public void updateAppTask_whenAabReleaseAvailable_redirectsToPlay() throws Exception {
-    TestOnProgressListener listener = new TestOnProgressListener(1);
+    TestOnProgressListener listener = TestOnProgressListener.withExpectedCount(1);
     UpdateTask updateTask = aabUpdater.updateAab(TEST_RELEASE_NEWER_AAB_INTERNAL);
     updateTask.addOnProgressListener(testExecutor, listener);
 

firebase-appdistribution/src/test/java/com/google/firebase/appdistribution/impl/TestOnProgressListener.java

@@ -23,7 +23,7 @@
 import java.util.concurrent.TimeUnit;
 
 /**
- * Helper listener that awaits a specific number of progress events on a {@code UpdateTask}.
+ * Helper listener that awaits a specific number of progress events on an {@code UpdateTask}.
  *
  * <p>This works around a limitation of the Tasks API where await() cannot be called on the main
  * thread. This listener works around it by running itself on a different thread, thus allowing the
@@ -38,11 +38,15 @@ class TestOnProgressListener implements OnProgressListener {
   private final CountDownLatch latch;
   private final List<UpdateProgress> progressUpdates = new ArrayList<>();
 
-  TestOnProgressListener(int expectedProgressCount) {
+  private TestOnProgressListener(int expectedProgressCount) {
     this.expectedProgressCount = expectedProgressCount;
     this.latch = new CountDownLatch(expectedProgressCount);
   }
 
+  static TestOnProgressListener withExpectedCount(int expectedCount) {
+    return new TestOnProgressListener(expectedCount);
+  }
+
   @Override
   public void onProgressUpdate(@NonNull UpdateProgress updateProgress) {
     progressUpdates.add(updateProgress);