Testing ViewPager (and CursorLoader) with Robolectric

Question

Does anyone know how to test the following setup using Robolectric?

Fragment containing a ViewPager, data loaded with a CursorLoader.

With the code below, the CursorLoader is never pushed into the adapter for the view pager. I get stuck at the await() call.

EventsFragmentTest.java:

@RunWith(CustomRobolectricTestRunner.class)
public class EventsFragmentTest extends AbstractDbAndUiDriver
{
    // which element in the view pager we are testing
    private static final int           TEST_INDEX = 0;

    protected SherlockFragmentActivity mActivity;
    protected EventsFragment_          mFragment;

    @Override
    @Before
    public void setUp() throws Exception
    {
        // create activity to hold the fragment
        this.mActivity = CustomRobolectricTestRunner.getActivity();

        // create and start the fragment
        this.mFragment = new EventsFragment_();
    }

    @Test
    public void sanityTest()
    {
        // create an event
        final Event event = this.createEvent();

        // create mock cursor loader
        final Cursor cursor = this.createMockEventCursor(event);
        this.mFragment.setCursorLoader(mock(CursorLoader.class));
        when(this.mFragment.getCursorLoader().loadInBackground()).thenReturn(cursor);
        CustomRobolectricTestRunner.startFragment(this.mActivity, this.mFragment);

        await().atMost(5, SECONDS).until(this.isCursorLoaderLoaded(), equalTo(true));

        // check for data displayed
        final TextView title = this.getTextView(R.id.event_view_title);
        final TextView text = this.getTextView(R.id.event_view_text);

        // exists and visible is enough for now
        this.getImageView(R.id.event_view_image);

        assertThat(title.getText().toString(), equalTo(event.getTitle()));
        assertThat(text.getText().toString(), is(event.getText()));

        // clean up
        cursor.close();
    }

    @Override
    protected View getRootView()
    {
        return ((ViewPager) this.mFragment.getView().findViewById(R.id.events_pager)).getChildAt(TEST_INDEX);
    }

    private Callable<Boolean> isCursorLoaderLoaded()
    {
        return new Callable<Boolean>()
        {
            public Boolean call() throws Exception
            {
                return EventsFragmentTest.this.mFragment.isCursorLoaderLoaded(); // The condition that must be fulfilled
            }
        };
    }

    /**
     * Create an event
     * 
     * @return
     */
    protected Event createEvent()
    {
        // create a random event
        final Event event = new Event();
        event.setImage(null);
        event.setLink("/some/link/" + RandomUtils.getRandomString(5)); //$NON-NLS-1$
        event.setResourceUri("/rest/uri/" + RandomUtils.getRandomDouble()); //$NON-NLS-1$
        event.setText("this is a test object " + RandomUtils.getRandomString(5)); //$NON-NLS-1$
        return event;
    }

    protected Cursor createMockEventCursor(final Event event)
    {
        // Create a mock cursor.
        final Cursor cursor = new CursorWrapper(mock(MockCursor.class));

        when(cursor.getCount()).thenReturn(1);
        when(cursor.getString(cursor.getColumnIndexOrThrow(EventTable.COLUMN_TEXT))).thenReturn(event.getText());
        when(cursor.getString(cursor.getColumnIndexOrThrow(EventTable.COLUMN_TITLE))).thenReturn(event.getTitle());
        when(cursor.getString(cursor.getColumnIndexOrThrow(EventTable.COLUMN_IMAGE))).thenReturn(event.getImage());
        when(cursor.getString(cursor.getColumnIndexOrThrow(EventTable.COLUMN_LINK))).thenReturn(event.getLink());
        when(cursor.getString(cursor.getColumnIndexOrThrow(EventTable.COLUMN_RESOURCE_URI))).thenReturn(
                        event.getResourceUri());

        // return created event
        return cursor;
    }

}

EventsFragment.java

@EFragment(resName = "events_fragment")
public class EventsFragment extends SherlockFragment implements LoaderCallbacks<Cursor>
{
    @ViewById(R.id.events_pager)
    protected ViewPager             mPager;

    @ViewById(R.id.events_indicator)
    protected CirclePageIndicator   mIndicator;

    @Pref
    protected ISharedPrefs_         mPreferences;

    protected EventsFragmentAdapter pageAdapter;

    private CursorLoader            mCursorLoader;

    /**
     * initialise the cursoradapter and the cursor loader manager.
     */
    @AfterViews
    void init()
    {
        final SherlockFragmentActivity activity = this.getSherlockActivity();

        this.pageAdapter = new EventsFragmentAdapter(activity.getSupportFragmentManager(), null);
        this.mPager.setAdapter(this.pageAdapter);
        this.mIndicator.setViewPager(this.mPager);
        this.getLoaderManager().initLoader(this.mPager.getId(), null, this);
    }

    /* (non-Javadoc)
     * @see android.support.v4.app.LoaderManager.LoaderCallbacks#onCreateLoader(int, android.os.Bundle)
     */
    @Override
    public Loader<Cursor> onCreateLoader(final int arg0, final Bundle arg1)
    {
        if (this.mCursorLoader == null)
        {
            // set sort to newest first
            final String sortOrder = BaseColumns._ID + " DESC"; //$NON-NLS-1$

            this.mCursorLoader = new CursorLoader(this.getActivity(), EventContentProvider.CONTENT_URI,
                            EventTable.getProjection(), AbstractDbTable.getWhereCondition(null),
                            AbstractDbTable.getWhereArgs(this.mPreferences, null), sortOrder);
        }
        return this.mCursorLoader;
    }

    /* (non-Javadoc)
     * @see android.support.v4.app.LoaderManager.LoaderCallbacks#onLoadFinished(android.support.v4.content.Loader, java.lang.Object)
     */
    @Override
    public void onLoadFinished(final Loader<Cursor> arg0, final Cursor cursor)
    {
        this.pageAdapter.swapCursor(cursor);

    }

    /* (non-Javadoc)
     * @see android.support.v4.app.LoaderManager.LoaderCallbacks#onLoaderReset(android.support.v4.content.Loader)
     */
    @Override
    public void onLoaderReset(final Loader<Cursor> arg0)
    {
        this.pageAdapter.swapCursor(null);
    }

    /**
     * Required for testing only.
     * 
     * @param cursorLoader
     */
    public void setCursorLoader(final CursorLoader cursorLoader)
    {
        this.mCursorLoader = cursorLoader;
    }

    /**
     * Required for testing only.
     * 
     * @param cursorLoader
     */
    public CursorLoader getCursorLoader()
    {
        return this.mCursorLoader;
    }

    public boolean isCursorLoaderLoaded()
    {
        return (this.pageAdapter.getCursor() != null);
    }
}

Answer 1

I'm not certain, but I would wager that the internal code is trying to use an AsyncTask to invoke the cursor loader's loadInBackground() method. You might be seeing a deadlock because the AsyncTask tries to invoke onPostExecute(). That call will try to run in your main UI thread, which happens to be the thread of your test routine. That can never happen because you are stuck in a wait with your test routine on the call stack.

Try moving your mocking up to a higher level so that nothing really happens in the background from the test. google `AsyncTask unit test android deadlock' to see examples where other people ran into similar problems.