CountDownLatchInAsyncTaskUnitTest.java

 /** 
 * This demonstrates how to test AsyncTasks in android JUnit. Below I used  
 * an in line implementation of a asyncTask, but in real life you would want 
 * to replace that with some task in your application. 
 * @throws Throwable  
 */ 
public void testSomeAsynTask () throws Throwable {
    // create  a signal to let us know when our task is done. 
    final CountDownLatch signal = new CountDownLatch(1);
 
    /* Just create an in line implementation of an asynctask. Note this  
     * would normally not be done, and is just here for completeness. 
     * You would just use the task you want to unit test in your project.  
     */ 
    final AsyncTask<String, Void, String> myTask = new AsyncTask<String, Void, String>() {
 
        @Override 
        protected String doInBackground(String... arg0) {
            //Do something meaningful. 
            return "something happened!"; 
        } 
 
        @Override 
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
 
            /* This is the key, normally you would use some type of listener 
             * to notify your activity that the async call was finished. 
             *  
             * In your test method you would subscribe to that and signal 
             * from there instead. 
             */ 
            signal.countDown();
        } 
    }; 
 
    // Execute the async task on the UI thread! THIS IS KEY! 
    runTestOnUiThread(new Runnable() {
 
        @Override 
        public void run() { 
            myTask.execute("Do something");                
        } 
    });        
 
    /* The testing thread will wait here until the UI thread releases it 
     * above with the countDown() or 30 seconds passes and it times out. 
     */         
    signal.await(30, TimeUnit.SECONDS);
 
    // The task is done, and now you can assert some things! 
    assertTrue("Happiness", true); 
}