TDD for Android 

Why do we test? •Testing ensure the Quality of the product; •Tests help improve design code; •Tests check that code works; 

Observations • Huge activities / fragments • Hard to add a new feature • Hard to test • Many apps tested in manual way • Fragmentation • Slow Android tests • Required device • Robolectric • Espresso • etc 

Bad vs Good tests @Test public void test1() { mPresenter.attachView(null); mPresenter.convertTemperature(); mPresenter.detachView(); verify(mView, never()).getInputValue(); verify(mView, never()).getFromTemperatureUnit(); verify(mView, never()).getToTemperatureUnit(); verify(mView, never()).setOutputValue(anyDouble()); when(mTemperatureFactory.getTemperatureConverter()) .thenReturn(mConverter); doNothing().when(mConverter).convertData(any(InputData.class)); mPresenter.attachView(mView); mPresenter.convertTemperature(); mPresenter.detachView(); verify(mEventBus).register(any()); verify(mView).displayProgress(); verify(mView, times(1)).getInputValue(); verify(mView, times(1)).getFromTemperatureUnit(); verify(mView, times(1)).getToTemperatureUnit(); verify(mEventBus).unregister(any()); } @Test public void shouldVerifyConvertDataSuccessful () { mPresenter.attachView(mView); mPresenter.convertTemperature(); mPresenter.detachView(); verify(mEventBus).register(any()); ... } @Test public void shouldVerifyConvertDataWithNullView() { mPresenter.attachView(null); mPresenter.convertTemperature(); mPresenter.detachView(); verify(mView, never()).getInputValue(); ... } Don’t Do 

Bad vs Good UI tests @Test public void shouldVerifyGravity() { View view = ...; assertEquals(Gravity.START, view.getForegroundGravity()); ... } @Test public void shouldVerifyOrderCoffee() { onView(withId(R.id.name_edit)) .perform(typeText("User"), closeSoftKeyboard()); onView(withId(R.id.pay)) .perform(click()); onView(withId(R.id.detail_text)) .check(matches(isDisplayed())); } Don’t Do 

Value 

What is Test Driven Development (TDD) Green Refactor Red 

Code separations Android App Core Acceptance tests Unit tests 

Model-View-Presenter View Presenter Model 

Application overview Web service Local 

Application overview Presenter Use case Repository Web service Local 

Recommendation for setting up the device / emulator One small recommendation for avoiding flakiness is turning off animation on real or virtual devices. • Window animation scale • Transition animation scale • Animator duration scale • Settings / Developer Options/ 

Hamcrest library 

Hamcrest + Espresso public static Matcher withToolbarTitle(final Matcher textMatcher) { return new BoundedMatcher(Toolbar.class) { @Override public boolean matchesSafely(Toolbar toolbar) { return textMatcher.matches(toolbar.getTitle()); } @Override public void describeTo(Description description) { description.appendText("with toolbar title: ") textMatcher.describeTo(description); } }; } onView(withId(R.id.toolbar)) .check(matches(withToolbarTitle( is (TITLE)))); startsWith endsWith ... 

UI test @RunWith(AndroidJUnit4.class) public class TemperatureConverterActivityTest { @Test public void shouldVerifyConvertingFromCelsiusToFahrenheit() { onView(withId(R.id.inputView)) .perform(typeText(String.valueOf(CELSIUS_VALUE)), closeSoftKeyboard()); setTemperatureUnit(R.id.inputTemperatureSpinner, CELSIUS_STR); setTemperatureUnit(R.id.outputTemperatureSpinner, FAHRENHEIT_STR); onView(withId(R.id.convertButton)) .perform(click()); onView(withId(R.id.outputView)) .check(matches(isDisplayed())); onView(withId(R.id.outputView)) .check(matches(withText(getOutputString(FAHRENHEIT_VALUE)))); } } 

Presenter test @RunWith(MockitoJUnitRunner.class) public class TemperatureConverterPresenterTest { @Mock TemperatureConverterView mView; … private TemperatureConverterPresenter mPresenter; @Test public void shouldVerifyConvertDataSuccessfulWithCorrectView() { mPresenter.attachView(mView); mPresenter.convertTemperature(); mPresenter.detachView(); verify(mEventBus).register(any()); ... } } 

Asynchronous calls using Mockito (Retrofit2) @RunWith(MockitoJUnitRunner.class) public class OnlineConverterTemperatureTest { private OnlineConverterTemperature mConverter; @Mock EventBus mEventBus; @Mock TemperatureConverterApiService mApiService; @Mock Call mCall; @Mock ResponseBody mResponseBody; @Captor ArgumentCaptor> argumentCapture; @Test public void shouldGetConvertedResult() { when(mApiService.getConvertedData(anyString(), anyString(), anyString())) .thenReturn(mCall); Response response = Response.success(mConvertedResult); mConverter.convertData(mInputData); verify(mCall).enqueue(argumentCapture.capture()); argumentCapture.getValue().onResponse(null, response); verify(mEventBus).post(new TemperatureConvertedSuccessful(mConvertedResult)); } } 

Testing system stuff • Notifications; • Press hardware buttons; • Interacting with any applications. UI Automator 

Continuous Integration (CIRCLE CI) circle.yml 

Testing tips 

Focus on App behaviour 

Use available stuff 

Use hamcrest library 

Do not copy your code between tests 

Launch directly desire screen 

Many small tests are better that big ones 

Test your code, not using libraries 

Test-Driven Development is NOT a silver bullet 

Thank you 1. Getting Started with Testing (Android) https://developer.android.com/training/testing/start/index.html 2. Espresso https://google.github.io/android-testing-support-library/docs/espresso/ 3. Ui Automator https://developer.android.com/training/testing/ui-testing/uiautomator-testing.html 4. Robolectric http://robolectric.org/ 5. Project https://github.com/AlexZhukovich/TemperatureConverterTDD 6. Blog http://alexzh.com/ @Alex_Zhukovich