Para ilustrar mi último problema con la escritura de pruebas JUnit para mi aplicación de Android, escribí un ejemplo simple con dos actividades,StartActivityForResult yChildActivity. El primero contiene unaTextView (para fines de visualización) y unButton mientras que el último contiene sólo unaButton. losonClickListener para el botón enStartActivityForResult simplemente comienza una instancia deChildActivity.

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);
    }
};

Ahora quiero probar este método usando JUnit. Así que escribí la siguiente prueba:

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<StartActivityForResult> {

    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); // <------ 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();
}

Ejecutando esta prueba da el siguiente resultado:

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$ 

Por lo que puedo decir, llamandostartButton.performClick() no comienza una instancia deChildActivity. ¿Lo que da?