I am trying to write Unit test cases for Activities in my app by extending the test class with ActivityUnitTestCase. I could successfully run the test cases earlier but now I'm always getting the exception while running them. Even though I'm pretty familiar with handling NullPointerExceptions, I couldn't figure out the problem that's causing this. I couldn't find any similar questions so I'm posting this one.
Stack trace shows me there is a null object reference at this line in my code
activity = startActivity(mIntent, null, null);
But the startActivity method is supposed to get the instance of the activity I'm testing. I'm not sure why it's returning null.
Here is the Stack trace.
java.lang.NullPointerException: Attempt to write to field 'android.os.IBinder android.app.ActivityThread.mLastIntendedActivityToken' on a null object reference
at android.app.Activity.performCreate(Activity.java:6372)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.support.test.runner.MonitoringInstrumentation.callActivityOnCreate(MonitoringInstrumentation.java:346)
at android.test.ActivityUnitTestCase.startActivity(ActivityUnitTestCase.java:158)
at com.abc.test.MainActivityTest.access$100(MainActivityTest.java:16)
at com.abc.test.MainActivityTest$1.run(MainActivityTest.java:34)
at android.app.Instrumentation$SyncRunnable.run(Instrumentation.java:1891)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6117)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
Test running failed: Instrumentation run failed due to 'java.lang.NullPointerException'
Here is the Test class
public class MainActivityTest extends ActivityUnitTestCase<MainActivity>{
private Intent mIntent;
private MainActivity activity;
public MainActivityTest() {
super(MainActivity.class);
}
@Override
protected void setUp() throws Exception {
super.setUp();
//Create an intent to launch target Activity as it is not automatically started by Android Instrumentation
mIntent = new Intent(getInstrumentation().getContext(), MainActivity.class);
//Start the activity under test in isolation, in the main thread to avoid assertion error.
getInstrumentation().runOnMainSync(new Runnable() {
@Override
public void run() {
activity = startActivity(mIntent, null, null);
}
});
}
@Override
protected void tearDown() throws Exception {
super.tearDown();
}
/**
* Tests the preconditions of this test fixture.
*/
@SmallTest
public void testPreconditions() {
assertNotNull("MainActivity is null", getActivity());
}
@MediumTest
public void testSecondActivityWasLaunchedWithIntent() {
// Get the intent for the next started activity
final Intent launchIntent = getStartedActivityIntent();
//Verify the intent was not null.
assertNotNull("Intent was null", launchIntent);
//Verify that LaunchActivity was finished
assertTrue(isFinishCalled());
}
}