Android AsyncTask testing with Android Test Framework

user_209310 0
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I have a very simple AsyncTask implementation example and am having problem in testing it using Android JUnit framework.

It works just fine when I instantiate and execute it in normal application. However when it's executed from any of Android Testing framework classes (i.e. AndroidTestCase, ActivityUnitTestCase, ActivityInstrumentationTestCase2 etc) it behaves strangely:

  • It executes doInBackground() method correctly
  • However it doesn't invokes any of its notification methods (onPostExecute(), onProgressUpdate(), etc) -- just silently ignores them without showing any errors.

This is very simple AsyncTask example:

package kroz.andcookbook.threads.asynctask;

import android.os.AsyncTask;
import android.util.Log;
import android.widget.ProgressBar;
import android.widget.Toast;

public class AsyncTaskDemo extends AsyncTask<Integer, Integer, String> {

AsyncTaskDemoActivity _parentActivity;
int _counter;
int _maxCount;

public AsyncTaskDemo(AsyncTaskDemoActivity asyncTaskDemoActivity) {
    _parentActivity = asyncTaskDemoActivity;
}

@Override
protected void onPreExecute() {
    super.onPreExecute();
    _parentActivity._progressBar.setVisibility(ProgressBar.VISIBLE);
    _parentActivity._progressBar.invalidate();
}

@Override
protected String doInBackground(Integer... params) {
    _maxCount = params[0];
    for (_counter = 0; _counter <= _maxCount; _counter++) {
        try {
            Thread.sleep(1000);
            publishProgress(_counter);
        } catch (InterruptedException e) {
            // Ignore           
        }
    }
}

@Override
protected void onProgressUpdate(Integer... values) {
    super.onProgressUpdate(values);
    int progress = values[0];
    String progressStr = "Counting " + progress + " out of " + _maxCount;
    _parentActivity._textView.setText(progressStr);
    _parentActivity._textView.invalidate();
}

@Override
protected void onPostExecute(String result) {
    super.onPostExecute(result);
    _parentActivity._progressBar.setVisibility(ProgressBar.INVISIBLE);
    _parentActivity._progressBar.invalidate();
}

@Override
protected void onCancelled() {
    super.onCancelled();
    _parentActivity._textView.setText("Request to cancel AsyncTask");
}

}

This is a test case. Here AsyncTaskDemoActivity is a very simple Activity providing UI for testing AsyncTask in mode:

package kroz.andcookbook.test.threads.asynctask;
import java.util.concurrent.ExecutionException;
import kroz.andcookbook.R;
import kroz.andcookbook.threads.asynctask.AsyncTaskDemo;
import kroz.andcookbook.threads.asynctask.AsyncTaskDemoActivity;
import android.content.Intent;
import android.test.ActivityUnitTestCase;
import android.widget.Button;

public class AsyncTaskDemoTest2 extends ActivityUnitTestCase<AsyncTaskDemoActivity> {
AsyncTaskDemo _atask;
private Intent _startIntent;

public AsyncTaskDemoTest2() {
    super(AsyncTaskDemoActivity.class);
}

protected void setUp() throws Exception {
    super.setUp();
    _startIntent = new Intent(Intent.ACTION_MAIN);
}

protected void tearDown() throws Exception {
    super.tearDown();
}

public final void testExecute() {
    startActivity(_startIntent, null, null);
    Button btnStart = (Button) getActivity().findViewById(R.id.Button01);
    btnStart.performClick();
    assertNotNull(getActivity());
}

}

All this code is working just fine, except the fact that AsyncTask doesn't invoke it's notification methods when executed by within Android Testing Framework. Any ideas?

junit android
8 Answers

The way to deal with this is to run any code that invokes an AsyncTask in runTestOnUiThread():

public final void testExecute() {
    startActivity(_startIntent, null, null);
    runTestOnUiThread(new Runnable() {
        public void run() {
            Button btnStart = (Button) getActivity().findViewById(R.id.Button01);
            btnStart.performClick();
        }
    });
    assertNotNull(getActivity());
    // To wait for the AsyncTask to complete, you can safely call get() from the test thread
    getActivity()._myAsyncTask.get();
    assertTrue(asyncTaskRanCorrectly());
}

By default junit runs tests in a separate thread than the main application UI. AsyncTask's documentation says that the task instance and the call to execute() must be on the main UI thread; this is because AsyncTask depends on the main thread's Looper and MessageQueue for its internal handler to work properly.

NOTE:

I previously recommended using @UiThreadTest as a decorator on the test method to force the test to run on the main thread, but this isn't quite right for testing an AsyncTask because while your test method is running on the main thread no messages are processed on the main MessageQueue — including the messages the AsyncTask sends about its progress, causing your test to hang.

user_1956910

How about using join?

fun myTest() = runBlocking {
    CoroutineScope(Dispatchers.IO).launch {
        // test something here
    }.join()
}
user_11293320
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