单元测试-为什么我的单元测试在使用finish（），处理程序和线程的代码上失败？

Question

Here is the activity I am testing. I wish I could write it the other way since I heard using thread.sleep is dangerous. But I'm not allowed to do that.

Here is what this code does: when onCreate is called, MainActivity pauses for a couple of seconds, then it fires Activity2

  public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final Handler handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                goToAct2();
            }
        };

        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(3000);
                    handler.sendEmptyMessage(0);

                } catch (InterruptedException e) {}
            }
        }).start();

    }
    private void goToAct2(){

    Intent i = new Intent (this,Activity2.class);
    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    startActivity(i);
    finish();
    }
}

I want to test if MainActivity calls the correct Activity (which is Activity2). Here is the unit test code:

public class MainActivityTest extends
        ActivityInstrumentationTestCase2<MainActivity>
{

    MainActivity activity;

    public MainActivityTest()
    {
        super(MainActivity.class);
    }

    protected void setUp() throws Exception
    {
        super.setUp();
        activity=getActivity();
    }

    @UiThreadTest
    public void testOne()
    {
        ActivityMonitor Act2Monitor = getInstrumentation().addMonitor(Activity2.class.getName(), null, false);  
        getInstrumentation().callActivityOnCreate(activity, null);;
        assertEquals(1, Act2Monitor.getHits());
    }
}

I notice that:

1. If I discard the handler-thread part:

   calling goToAct2() directly in onCreate(), the test still fails. But if I delete finish() in that method, the test passes.

2. If I keep the handler-thread part:

   No matter what I do, the test keeps on failing even the actual activity works as it supposed to.

What is going on under the hood? And, how do I properly write a test that can confirm the creation of Activity2?

Answer 1

In your application activity code you should have something like this:

Intent i = new Intent(this, SecondActivity.class);
startActivityForResult(i, 1);

In activity2 set the data which you want to return back to FirstActivity.

Intent returnIntent = new Intent();
returnIntent.putExtra("result",result);
setResult(Activity.RESULT_OK,returnIntent);
finish();

Then in the main activity, override the onActivityResult method to process the result.

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

    if (requestCode == 1) {
        if(resultCode == Activity.RESULT_OK){
            String result=data.getStringExtra("result");
        }
        else {
            //Write your code if there's no result
        }
    }
}

Finally, in your test case use the class ActivityUnitTestCase and call either the isFinishCalled() or getFinishedActivityRequest() to inspect the parameters that they were called with.

The documentation for this is at:

https://developer.android.com/reference/android/test/ActivityUnitTestCase.html#isFinishCalled()

Answer 2

I cannot create a comment so I have to post this as an asnwer sorry.

From what I read you need to call the getActivity() after the finish() method has been called.

Meanning the instance you have stored in activity is not the new activity but the one that got destroy. I would sugest trying to change getInstrumentation().callActivityOnCreate(activity, null); to getInstrumentation().callActivityOnCreate(getActivity(), null); This should return the current activity and not the one that has been destroyed.

Hope it helps.