title: Call waitForMonitorWithTimeout() from a @UiThreadTest
body: <p>To illustrate my latest problem with writing JUnit tests for my Android app, I wrote a simple example with two activities, <code>StartActivityForResult</code> and <code>ChildActivity</code>. The former contains a <code>TextView</code> (for display purposes) and a <code>Button</code> while the later contains just a <code>Button</code>. The <code>onClickListener</code> for the button in <code>StartActivityForResult</code> simply starts an instance of <code>ChildActivity</code>.</p>
  
  <pre><code>private View.OnClickListener onStart = new View.OnClickListener() {
      @Override
      public void onClick(View view) {
          Log.d(TAG, "Start button clicked");
          Intent intent = new Intent(StartActivityForResult.this, ChildActivity.class);
  
          StartActivityForResult.this.startActivityForResult(intent, R.id.child_request);
      }
  };
  </code></pre>
  
  <p>Now I want to test this method using JUnit. So I wrote the following test:</p>
  
  <pre><code>package codeguru.startactivityforresult;
  
  import android.app.Activity;
  import android.app.Instrumentation;
  import android.content.Intent;
  import android.test.ActivityInstrumentationTestCase2;
  import android.test.UiThreadTest;
  import android.util.Log;
  import android.widget.Button;
  import android.widget.TextView;
  import junit.framework.Assert;
  
  public class StartActivityForResultTest extends ActivityInstrumentationTestCase2&lt;StartActivityForResult&gt; {
  
      public StartActivityForResultTest() {
          super(StartActivityForResult.class);
      }
  
      @Override
      public void setUp() throws Exception {
          super.setUp();
  
          Log.d(TAG, "setUp()");
  
          this.setActivityInitialTouchMode(false);
  
          this.activity = this.getActivity();
          this.resultText = (TextView) this.activity.findViewById(R.id.result_text);
          this.startButton = (Button) this.activity.findViewById(R.id.start_button);
  
          Intent data = new Intent();
          data.putExtra(this.activity.getString(R.string.result), RESULT);
          Instrumentation.ActivityResult result = new Instrumentation.ActivityResult(Activity.RESULT_OK, data);
  
          this.childMonitor = new Instrumentation.ActivityMonitor(ChildActivity.class.getName(), result, true);
          this.getInstrumentation().addMonitor(this.childMonitor);
      }
  
      @Override
      public void tearDown() throws Exception {
          this.activity.finish();
  
          super.tearDown();
      }
  
      @UiThreadTest
      public void testStartButtonOnClick() {
          Assert.assertTrue(this.startButton.performClick());
  
          Activity childActivity = this.getInstrumentation().waitForMonitorWithTimeout(this.childMonitor, TIME_OUT);
          Assert.assertNotNull(childActivity); // &lt;------ Line 51
  
          Button resultButton = (Button) childActivity.findViewById(R.id.result_button);
          Assert.assertTrue(resultButton.performClick());
  
          Assert.assertEquals(Integer.toString(RESULT), this.resultText.getText().toString());
      }
      private Activity activity = null;
      private TextView resultText = null;
      private Button startButton = null;
      private Instrumentation.ActivityMonitor childMonitor = null;
      private static final int TIME_OUT = 5 * 1000; // 5 seconds
      private static final int RESULT = 69;
      private static final String TAG = StartActivityForResultTest.class.getName();
  }
  </code></pre>
  
  <p>Running this test gives the following output:</p>
  
  <pre><code>codeguru@trolloc:~/src/java/stackoverflow/sscce/StartActivityForResult/test$ adb logcat -c
  codeguru@trolloc:~/src/java/stackoverflow/sscce/StartActivityForResult/test$ adb shell am instrument -w -e class codeguru.startactivityforresult.StartActivityForResultTest codeguru.startactivityforresult.tests/android.test.InstrumentationTestRunner
  
  codeguru.startactivityforresult.StartActivityForResultTest:
  Failure in testStartButtonOnClick:
  junit.framework.AssertionFailedError
      at codeguru.startactivityforresult.StartActivityForResultTest.testStartButtonOnClick(StartActivityForResultTest.java:51)
      at java.lang.reflect.Method.invokeNative(Native Method)
      at android.test.InstrumentationTestCase.runMethod(InstrumentationTestCase.java:214)
      at android.test.InstrumentationTestCase.access$000(InstrumentationTestCase.java:36)
      at android.test.InstrumentationTestCase$2.run(InstrumentationTestCase.java:189)
      at android.app.Instrumentation$SyncRunnable.run(Instrumentation.java:1602)
      at android.os.Handler.handleCallback(Handler.java:615)
      at android.os.Handler.dispatchMessage(Handler.java:92)
      at android.os.Looper.loop(Looper.java:137)
      at android.app.ActivityThread.main(ActivityThread.java:4745)
      at java.lang.reflect.Method.invokeNative(Native Method)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
      at dalvik.system.NativeStart.main(Native Method)
  
  Test results for InstrumentationTestRunner=.F
  Time: 3.248
  
  FAILURES!!!
  Tests run: 1,  Failures: 1,  Errors: 0
  
  
  codeguru@trolloc:~/src/java/stackoverflow/sscce/StartActivityForResult/test$ adb logcat -d codeguru.startactivityforresult.StartActivityForResultTest:D codeguru.startactivityforresult.StartActivityForResult:D codeguru.startactivityforresult.ChildActivity:D *:S
  D/codeguru.startactivityforresult.StartActivityForResultTest(  954): setUp()
  D/codeguru.startactivityforresult.StartActivityForResult(  954): onCreate()
  D/codeguru.startactivityforresult.StartActivityForResult(  954): Start button clicked
  layne@trolloc:~/src/java/stackoverflow/sscce/StartActivityForResult/test$ 
  </code></pre>
  
  <p>As far as I can tell, calling <code>startButton.performClick()</code> doesn't start an instance of <code>ChildActivity</code>. What gives?</p>