How to test Handler in Android?

Testing a Handler in Android is essential for ensuring that your background tasks are managed effectively. A Handler allows you to send and process Message and Runnable objects associated with a thread's MessageQueue. Below is a simple example of how to test a Handler using the Android instrumentation framework.


            // MainActivity.java
            public class MainActivity extends AppCompatActivity {
                private Handler handler;
                private TextView textView;

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

                    handler = new Handler(Looper.getMainLooper()) {
                        @Override
                        public void handleMessage(Message msg) {
                            textView.setText("Handler Message Received");
                        }
                    };
                }

                public void sendMessageToHandler() {
                    Message message = Message.obtain();
                    handler.sendMessage(message);
                }
            }

            // MainActivityTest.java
            @RunWith(AndroidJUnit4.class)
            public class MainActivityTest {
                private MainActivity mainActivity;

                @Before
                public void setup() {
                    mainActivity = ActivityScenario.launch(MainActivity.class).getResult().getActivity();
                }

                @Test
                public void testHandler() {
                    mainActivity.sendMessageToHandler();
                    onView(withId(R.id.textView)).check(matches(withText("Handler Message Received")));
                }
            }

Android Handler Testing Instrumentation MessageQueue Background Tasks

How to test Handler in Android?

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