Unit test for display notif with NSE and foreground handler

When the NSE calls `complete` with `notification.mutableCopy()` rather than the original notification, and the foreground handler is also set, the notification will not display.

This test is added to replicate that behavior. We will address the bug in the following commit to get the test to pass.

Author: nan-li

OneSignalSDK/unittest/src/test/java/com/test/onesignal/GenerateNotificationRunner.java

@@ -1983,6 +1983,64 @@ public void remoteNotificationReceived(Context context, OSNotificationReceivedEv
       }
    }
 
+   @Test
+   @Config(shadows = { ShadowGenerateNotification.class })
+   public void testNotificationProcessingAndForegroundHandler_callCompleteWithMutableNotification_displays() throws Exception {
+      // 1. Setup correct notification extension service class
+      startRemoteNotificationReceivedHandlerService(
+              RemoteNotificationReceivedHandler_notificationReceivedCallCompleteWithMutableNotification
+                      .class
+                      .getName()
+      );
+
+      // 2. Init OneSignal
+      OneSignal.setAppId("b2f7f966-d8cc-11e4-bed1-df8f05be55ba");
+      OneSignal.initWithContext(blankActivity);
+      OneSignal.setNotificationWillShowInForegroundHandler(notificationReceivedEvent -> {
+         lastForegroundNotificationReceivedEvent = notificationReceivedEvent;
+
+         // Call complete to end without waiting default 30 second timeout
+         notificationReceivedEvent.complete(notificationReceivedEvent.getNotification());
+      });
+      threadAndTaskWait();
+
+      blankActivityController.resume();
+      threadAndTaskWait();
+
+      // 3. Receive a notification in foreground
+      FCMBroadcastReceiver_processBundle(blankActivity, getBaseNotifBundle());
+      threadAndTaskWait();
+
+      // 4. Make sure service was called
+      assertNotNull(lastServiceNotificationReceivedEvent);
+
+      // 5. Make sure foreground handler was called
+      assertNotNull(lastForegroundNotificationReceivedEvent);
+
+      // 6. Make sure running on main thread check is called, this is only called for showing the notification
+      assertTrue(ShadowGenerateNotification.isRunningOnMainThreadCheckCalled());
+
+      // 7. Check badge count to represent the notification is displayed
+      assertEquals(1, ShadowBadgeCountUpdater.lastCount);
+   }
+
+   /**
+    * @see #testNotificationProcessingAndForegroundHandler_callCompleteWithMutableNotification_displays
+    */
+   public static class RemoteNotificationReceivedHandler_notificationReceivedCallCompleteWithMutableNotification implements OneSignal.OSRemoteNotificationReceivedHandler {
+
+      @Override
+      public void remoteNotificationReceived(final Context context, OSNotificationReceivedEvent receivedEvent) {
+         lastServiceNotificationReceivedEvent = receivedEvent;
+
+         OSNotification notification = receivedEvent.getNotification();
+         OSMutableNotification mutableNotification = notification.mutableCopy();
+
+         // Complete is called to end NotificationProcessingHandler
+         receivedEvent.complete(mutableNotification);
+      }
+   }
+
    @Test
    @Config(shadows = { ShadowGenerateNotification.class })
    public void testNotificationWillShowInForegroundHandlerIsCallWhenReceivingNotificationInForeground() throws Exception {