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Test-Driven Android Development at GDG Devfest Istanbul 2014

Test-Driven Android Development at GDG Devfest Istanbul 2014

Everybody knows testing is important, so let’s focus on test-driven development, testing best practices and the most useful Android testing libraries in our quest to improve the user experience and developer happiness. In this talk you'll get an overview of how several types of testing (unit, integration, UI testing) fit into an Android project. The Android team has improved the testing story for Android during the years, but the Android testing framework can be complemented with several other tools and libraries to help you build better quality applications. And let's not forget that the ease and thoroughness of your testing is also determined by the architecture of your application. We'll show you how to get the most out of Android's testing infrastructure, in order to enable you to build great quality apps.


Filip Maelbrancke

December 06, 2014


  1. Test-Driven Android Development

  2. Testing

  3. Android & Testing 01 02 03 Why? What? How?

  4. None
  5. None
  6. None
  7. Your host Filip Maelbrancke Consultant @ AppFoundry filip.maelbrancke@appfoundry.be @fmaelbrancke

  8. None
  9. Testing Avoid problems

  10. TESTING Manual testing is tedious Humans are not very good

    at testing But computers are...
  11. “Computers are designed to do simple repetitive tasks. The second

    you have humans doing repetitive tasks, all the computers get together late at night and laugh at you...” Neil Ford
  12. Manual vs Automated

  13. Manual vs Automated

  14. Manual vs Automated

  15. Mitigate issues? Be pro-active… and test.

  16. EXCUSES We never make mistakes! The functionality is trivial Tests

    slow us down Management won’t let us WE = HERO TRIVIAL SLOW MANAGEMENT ǩ

  18. Repeatability (no matter what development stack he uses) in which

    they are being run Tests need to be run by every developer ♂ Tests must not rely on the environment
  19. Speed The shorter, the less distraction less of an interruption

    to our workflow
  20. Speed The shorter, the less distraction less of an interruption

    to our workflow
  21. Self-documenting Testable code = clear Testable code = easy to

    follow we can just look at the test No need to explain how a component works No need to write documentation tests = usage examples
  22. Tests should also be … Easy to execute Easy to

    debug Realistic Fluent API
  23. Unit tests are real measure of project health and code

  24. Android dev

  25. Test types Unit tests Ŷ Functional tests Ŷ Acceptance tests

    Ŷ Integration tests Ŷ Regression tests Ŷ
  26. d.android.com

  27. Instrumentation Process Test package InstrumentationTestRunner Application package Test case classes

  28. Instrumentation Test Activity state saving and restoration // Start the

    main activity of the application under test
 mActivity = getActivity();
 // Get a handle to the Activity object's main UI widget, a Spinner
 mSpinner = (Spinner)mActivity.findViewById(com.android.example.spinner.R.id.Spinner);
 // Set the Spinner to a known position
 // Stop the activity - The onDestroy() method should save the state of the Spinner
 // Re-start the Activity - the onResume() method should restore the state of the Spinner
 mActivity = getActivity();
 // Get the Spinner's current position
 int currentPosition = mActivity.getSpinnerPosition();
 // Assert that the current position is the same as the starting position
 assertEquals(TEST_STATE_DESTROY_POSITION, currentPosition);
  29. Testing demo Simple master-detail app ☼

  30. Assert! Don’t assume Ŷ Assert Ŷ

  31. Assert assertEquals assertTrue assertFalse fail assertNull assertNotSame assertSame assertNotNull Assert

  32. ViewAssertions

  33. Expressiveness 

  34. Hamcrest assertThat(audience, is(payingAttention())) Verification Mocking Assertions

  35. Hamcrest Library of matchers Ŷ Syntactic sugar Ŷ Assert assertThat(someString,

    is(equalTo(“Expected”))); actual value expectation on the value (Matcher)
  36. Hamcrest Assert Hamcrest assertEquals(“Conversion failed”, “Expected”, someString); assertThat(someString, is(equalTo(“Expected”)));

  37. Hamcrest: collections Assert assertEquals(person, bigbangCharacters.getPersons().iterator().next()); Hamcrest assertThat(bigbangCharacters.getPersons(), hasItem(person));

  38. Hamcrest matchers Core anything
 … Logical allOf

    Object equalTo
 (not)nullValue Custom Beans hasProperty Text equalToIgnoringCase
 … Number greaterThan(OrEqualTo)
 closeTo Collections hasItem, hasItems
  39. View Matchers Hamcrest Ŷ allOf() / anyOf() ➪ give more

    power Ŷ TestRunner // assert that textview does not start with with "XYZ" and contains "ABC" anywhere
 .check(matches(allOf(withText(not(startsWith("XYZ"))), withText(containsString("ABC")))));
 // assert that textview ends with "XYZ" or contains "ABC" anywhere
 .check(matches(anyOf(withText(endsWith("XYZ")), withText(containsString("ABC")))));
  40. Hamcrest Lots of useful matchers Ŷ Custom matchers Ŷ not

    a number public void testSquareRootOfMinusOneIsNotANumber() {
 assertThat(Math.sqrt(-1), is(notANumber()));
  41. Hamcrest custom matcher Hamcrest matcher /**
 * Hamcrest matcher: test

    if a double has the value NaN (not a number)
 public class IsNotANumber extends TypeSafeMatcher<Double> {
 public boolean matchesSafely(Double number) {
 return number.isNaN();
 public void describeTo(Description description) {
 description.appendText("not a number");
 public static <T> Matcher<Double> notANumber() {
 return new IsNotANumber();
  42. None
  43. Espresso

  44. Espresso Easy API for test authors Find view Do stuff

    with view Check some state Without • waitUntil(timeout) • boilerplate
  45. Espresso API onView(Matcher<View>) onData(Matcher<Object>) onView(Matcher<View>) onView(Matcher<View>) withId() / withText() is()

    / instanceOf() click() / enterText() / scrollTo() matches(Matcher<View>) isDisplayed / isEnabled / hasFocus withText / … Find stuff Do stuff Check
  46. Espresso Espresso onView(withId(R.id.some_id)).perform(click()); 
 onView(withText("Hi there”)).check(matches(isDisplayed())); 

  47. Espresso API onView(Matcher<View>) onData(Matcher<Object>) Espresso withId() withText() ViewMatchers perform() check()

    ViewInteraction / DataInteraction click() enterText() scrollTo() ViewActions matches(Matcher<View>) doesNotExist() ViewAssertions find view to operate on composed of © Stephan Linzner (Google)
  48. View Matchers Espresso uses Hamcrest Matchers Espresso Matchers = Hamcrest

    Ŷ Make assertions on views Ŷ Filter views Ŷ Reuse existing Matchers Ŷ Create your own Matchers Ŷ from hamcrest-core and hamcrest-library
  49. View Matchers provides Android specific View Matchers ViewMatchers Ŷ •

    click() • scrollTo() • writeText() Basic view actions Ŷ
  50. Custom ViewAction Espresso ViewAction /**
 * Clears view text by

    setting {@link EditText}s text property to "".
 public class ClearTextAction implements ViewAction {
 public Matcher<View> getConstraints() {
 return allOf(isDisplayed(), isAssignableFrom(EditText.class));
 public void perform(UiController uiController, View view) {
 ((EditText) view).setText("");
 public String getDescription() {
 return "Clear the EditText component";
  51. Custom ViewAction Espresso ViewAction /**
 * Your own custom View

 public class CustomViewActions {
 private CustomViewActions() {
 * Returns an action that clears text on the view. Extra thoroughly!
 public static ViewAction clearTextExtraThoroughly() {
 return new ClearTextAction();
  52. Testing demo Testing a temperature converter ☼

  53. Use Custom ViewAction Espresso ViewAction public void testClearCelsiusTextField() {

  54. Reliability through synchronization between Instrumentation thread and UI thread for

    background resources Espresso synchronizes AsyncTasks default thread pool • wait until app is idle • perform operation on the UI thread • wait until completion • check result for custom implementations
 ThreadPool Synchronization Ŷ Synchronization Ŷ Synchronization Ŷ AsyncTask Ŷ IdlingResource interface Ŷ
  55. Espresso synchronization Espresso IdlingResource public class IdleMonitor implements IdlingResource {

 public String getName() {
 return IdleMonitor.class.getSimpleName();
 public boolean isIdleNow() {
 // return true if resource is idle
 return false;
 public void registerIdleTransitionCallback(ResourceCallback resourceCallback) {
 // store a reference to the resourceCallback
 // notify resourceCallback when idle
 } Espresso.registerIdlingResources(idlingResource);
  56. Robolectric

  57. Android testing AndroidTestCase needs an instance of the emulator to

    run • spin up emulator • deploy the APK • run the actual tests Big time sink: Ŷ
  58. Android testing Android core libraries depend upon the actual Android

    operating system
  59. Robolectric that would otherwise need an emulator / device (mock

    implementations of Android core libraries) too slow / hard for unit testing without the baggage of a device Replaces the behavior of code Ŷ Write JUnit tests Ŷ When? Ŷ Does this by using Shadow classes Ŷ InstrumentationTestCase Ŷ vs real device / speedy emulator Ŷ http://robolectric.org/
  60. Robolectric Robolectric 
 public class MyActivityTest {

    void clickingButton_shouldChangeResultsViewText() throws Exception {
 MyActivity activity = Robolectric.buildActivity(MyActivity.class).create().get();
 Button pressMeButton = (Button) activity.findViewById(R.id.press_me_button);
 TextView results = (TextView) activity.findViewById(R.id.results_text_view);
 String resultsText = results.getText().toString();
 assertThat(resultsText, equalTo("Testing Android Rocks!"));
  61. Robolectric setup • Robolectric • Novoda gradle-android-test-plugin see Paul Blundell

    Tests run inside the JVM Ŷ Gradle - Maven Ŷ Configure it yourself Ŷ Gradle plugin Ŷ http://blog.blundell-apps.com/android-gradle-app-with-robolectric-junit-tests/
  62. Robolectric setup

  63. Robolectric setup Robolectric setup apply plugin: 'java'
 dependencies {

    def androidModule = project(':appfoundry-app')
 compile androidModule
 testCompile rootProject.ext.libraries.junit
 testCompile rootProject.ext.libraries.robolectric
 testCompile androidModule.android.applicationVariants.toList().first().javaCompile.classpath
 testCompile androidModule.android.applicationVariants.toList().first().javaCompile.outputs.files
 testCompile files(androidModule.plugins.findPlugin("com.android.application").getBootClasspath())
  64. Robolectric Annotate your class @RunWith(RobolectricTestRunner.class)
 public class MyActivityTest {

 public void clickingButton_shouldChangeResultsViewText() throws Exception {
 MyActivity activity = Robolectric.buildActivity(MyActivity.class).create().get();
 Button pressMeButton = (Button) activity.findViewById(R.id.press_me_button);
 TextView results = (TextView) activity.findViewById(R.id.results_text_view);
 String resultsText = results.getText().toString();
 assertThat(resultsText, equalTo("Testing Android Rocks!"));
  65. Robolectric

  66. Android testing JUnit 4 Support JUnit 4 test @RunWith(JUnit4.class)

    class AndroidJUnit4Test {
 Conference devoxx;
 public void setUp() {
 devoxx = Conferences.newInstance(Conference.DEVOXX);
 public void tearDown() {
 public void testPreconditions() {
 assertThat(devoxx, is(notNullValue()));
 public void devoxxShouldBeGreat() {
 assertThat(devoxx, is(awesome()));
  67. Mocking & Stubbing

  68. Mockito in isolation Change runtime implementation Ŷ That can be

    predictably tested Ŷ Verify behaviour Ŷ Mockito Ŷ
  69. Mockito the behaviour of your components during a test Java

    mocking framework Ŷ Mock dependencies Ŷ Inject Mocks to validate Ŷ Mock function return values Ŷ https://code.google.com/p/mockito/
  70. Mockito Mockito @Test
 public void testMockedConverter() throws Exception {

 final float expected_result = 32.0f;
 // given
 ConverterActivity activity = Robolectric.buildActivity(ConverterActivity.class).create().get();
 activity.onCreate(new Bundle());
 EditText celsiusField = (EditText) activity.findViewById(R.id.celsius_textview);
 CelsiusFahrenheitConverter mockConverter = Mockito.mock(CelsiusFahrenheitConverter.class);
 // when
 Button convertButton = (Button) activity.findViewById(R.id.conversion_button);
 // then
 Mockito.verify(mockConverter, Mockito.times(1)).convertCelsiusToFahrenheit(Mockito.anyFloat());
 TextView fahrenheitField = (TextView) activity.findViewById(R.id.fahrenheit_textview);
 String fahrenheitString = fahrenheitField.getText().toString();
 assertThat(fahrenheitString, equalTo(String.valueOf(expected_result)));
  71. The Monkey

  72. evil monkey…

  73. Monkey pseudo-random stream of user events Generates events Ŷ clicks

    Ŷ touches Ŷ gestures Ŷ system-level events Ŷ Stress test your app Ŷ
  74. Monkey number of events to attempt operational constraints, such as

    restricting the test to a single package Event types and frequencies command-line tool Ŷ basic configuration Ŷ $ adb shell monkey -p your.package.name -v 500 Ŷ
  75. AssertJ Android for checking assertions to read / write http://square.github.io/assertj-android/

    Syntactic sugar Ŷ Extension of the AssertJ library Ŷ Makes tests easier Ŷ Fluent syntax Ŷ
  76. AssertJ Android Assertions for Android objects Ŷ + support libraries

  77. AssertJ Android Regular JUnit AssertJ Android assertEquals(View.GONE, view.getVisibility()); assertThat(view).isGone(); expected:

    <8> but was: <4> Expected visibility <gone> but was <invisible>.
  78. AssertJ Android Regular JUnit assertEquals(View.VISIBLE, layout.getVisibility()); assertEquals(VERTICAL, layout.getOrientation()); assertEquals(4, layout.getChildCount());

    assertEquals(SHOW_DIVIDERS_MIDDLE, layout.getShowDividers()); AssertJ Android assertThat(layout).isVisible() .isVertical() .hasChildCount(4) .hasShowDividers(SHOW_DIVIDERS_MIDDLE);
  79. Testing network resources

  80. Testing network resources Unit tests Ŷ Integration tests Ŷ Retrofit

  81. Testing network resources how to trigger edge cases like API

    rate limit exceeded? HTTP calls should be asynchronous … Hit a real server? Ŷ Brittle tests! Ŷ Slow tests Ŷ Network or server is down Ŷ Incomplete tests Ŷ Further complicated in Android Ŷ
  82. Testing network resources Use a test server Ŷ Mock the

    Retrofit interface Ŷ
  83. Using a test server • virtually no changes or code

    required in your app codebase • can be shared across multiple platforms (Android, iOS, web, …) • another dependency (that can fail) • something new to figure out • not always easy to trigger errors or edge cases • what if ‘state’ is needed? • ‘slow’ tests execution, still HTTP calls needed PROs Ŷ CONs Ŷ
  84. Mocking the Retrofit interface • robust: no network errors, timeouts,

    … • easy to generate errors / edge cases • easy to control server-side state • write your dummy data in Java • extra test code needed • you don’t test the JSON deserialization (but you can add unit tests) • mock a part of your application ➪ not a true integration test PROs Ŷ CONs Ŷ You trust the test suites of Retrofit, Gson, … and mock out the data
  85. Network testing Mock network interface ‘Fake’-‘real’ server

  86. Mocking the Retrofit interface MockRestAdapter sample

  87. Mocking the Retrofit interface Retrofit mock public interface GitHub {

 List<Contributor> contributors(@Path("owner") String owner, @Path("repo") String repo);
  88. Mocking the Retrofit interface Canned data /** A mock implementation

    of the {@link GitHub} API interface. */
 static class MockGitHub implements GitHub {
 private final Map<String, Map<String, List<Contributor>>> ownerRepoContributors;
 public MockGitHub() {
 ownerRepoContributors = new LinkedHashMap<String, Map<String, List<Contributor>>>();
 // Seed some mock data.
 addContributor("square", "retrofit", "John Doe", 12);
 addContributor("square", "retrofit", "Bob Smith", 2);
 addContributor("square", "retrofit", "Big Bird", 40);
 addContributor("square", "picasso", "Proposition Joe", 39);
 addContributor("square", "picasso", "Keiser Soze", 152);
  89. Mocking the Retrofit interface Mock @Override public List<Contributor> contributors(String owner,

    String repo) {
 Map<String, List<Contributor>> repoContributors = ownerRepoContributors.get(owner);
 if (repoContributors == null) {
 return Collections.emptyList();
 List<Contributor> contributors = repoContributors.get(repo);
 if (contributors == null) {
 return Collections.emptyList();
 return contributors;
  90. Mocking the Retrofit interface Mock // Create a very simple

    REST adapter which points the GitHub API endpoint.
 RestAdapter restAdapter = new RestAdapter.Builder()
 // Wrap our REST adapter to allow mock implementations and fake network delay.
 MockRestAdapter mockRestAdapter = MockRestAdapter.from(restAdapter);
 // Instantiate a mock object so we can interact with it later.
 MockGitHub mockGitHub = new MockGitHub();
 // Use the mock REST adapter and our mock object to create the API interface.
 GitHub gitHub = mockRestAdapter.create(GitHub.class, mockGitHub);
 // Query for some contributors for a few repositories.
 printContributors(gitHub, "square", "retrofit");
 printContributors(gitHub, "square", "picasso");
  91. Network testing Mock network interface ‘Fake’-‘real’ server

  92. MockWebServer predictable requests-responses Scriptable web server Ŷ okhttp (square) Ŷ

    Specify responses Ŷ Test HTTP clients Ŷ Verify requests Ŷ Like Mockito (for HTTP stack) Ŷ • script your mocks • run app code • verify that expected requests were made
  93. MockWebServer MockWebServer // Create a MockWebServer. These are lean enough

    that you can create // a new instance for every unit test. MockWebServer mockWebServer = new MockWebServer();
 // Setup the MockWebServer & schedule a response
 MockResponse mockResponse = new MockResponse();
 // Setup your networking lib. Ask the server for its url.
 … mockWebServer.getUrl(“/“);
  94. Wiremock predictable requests-responses wiremock.org Ŷ Tom Akehurst Ŷ Reproduce real-world

    scenarios Ŷ Increase reliability Ŷ Stateful scenarios Ŷ Non-Android specific Ŷ
  95. Wiremock via HTTP/JSON API • _admin/mappings/new • mappings folder HTTP

    server Ŷ configure responses Ŷ use with Java API Ŷ
  96. Wiremock Wiremock JSON API { "request": { "method": "GET", "url":

    "/api/mytest" }, "response": { "status": 200, "body": "More content\n" } } wiremock.org documentation
  97. Wiremock Wiremock Java API stubFor(get(urlEqualTo("/some/thing")) .willReturn(aResponse() .withStatus(404) .withBody(“No!!”))); wiremock.org documentation

  98. Wiremock Wiremock Java test @Test public void exampleTest() { //

    make your app do requests to http://localhost:8080 stubFor(get(urlEqualTo("/my/resource")) .willReturn(aResponse() .withStatus(200) .withBody("<response>Some content</response>"))); onView(withId(R.id.submit_button)).perform(click()); onView(withText(“error message”)).check(matches(isDisplayed())); verify(postRequestedFor(urlMatching(“/my/resource/[a-z0-9]+”))); } wiremock.org documentation
  99. Wiremock … out-of-the-box Android support is coming… Stateful Ŷ Errors

    / delays Ŷ Wiremock in the test APK Ŷ Wiremock as server on network Ŷ
  100. Application ARCHITECTURE

  101. None
  102. Software design patterns Good code = testable code Ŷ Dependency

    injection Ŷ
  103. Software design patterns Architecting Android Applications with Dagger Dependency injection

    Ŷ Dagger Ŷ Avoid reflection at runtime Ŷ Define dependencies Ŷ Jake Wharton Ŷ https://parleys.com/play/529bde2ce4b0e619540cc3ae
  104. Dependency injection Decoupling Ŷ Swap mocks in for tests Ŷ


  106. Automated distributed testing Automated distributed instrumentation testing Screenshots share with

    the designers…? in parallel Run tests on multiple devices Reports / logs captured for each test
  107. Spoon https://square.github.io/spoon/ Automate test execution Ŷ across multiple devices Ŷ

    Aggregation of screenshots Ŷ Aggregate the results Ŷ
  108. Spoon High level tests overview Ŷ Test failure specific Ŷ

    to a single device or all devices
  109. Spoon: device view Results of each test on one device

    Ŷ Useful for tracking down Ŷ device-specific failures of individual tests
  110. Spoon: test view Results of single test on all devices

  111. Spoon: screenshots Visual inspection of test execution Ŷ screenshots Spoon.screenshot(activity,

    "initial_state"); /* Normal test code... */ Spoon.screenshot(activity, "after_login"); http://square.github.io/spoon/sample/
  112. Build pipeline Checkout / compile Unit tests Test coverage Code

    analysis Create deployable artifact Deploy for automatic QA test Trigger automated QA stage
  113. Build pipeline tools Build (maven - gradle) Dependency repo (nexus

    - artifactory) Testing framework (JUnit - ...) Test coverage (Cobertura - Emma - Jacoco) Code analysis (Checkstyle, findbugs, pmd, Android Lint) Creation of deployable artifact (buildtool, artifact repo) Trigger next stage
  114. Continuous integration benefits without additional effort Fast feedback - fewer

    errors Ŷ Test everything on every (nightly) build Ŷ Regression tests Ŷ Less manual testing Ŷ
  115. Jenkins

  116. Jenkins

  117. Continuous integration • Jenkins • Bamboo Travis … Server Ŷ

    Hosted Ŷ https://travis-ci.org
  118. Test coverage open-source toolkit for measuring and reporting Java code

    coverage Metrics Ŷ Code safely Ŷ JaCoCo Ŷ Find risky code Ŷ
  119. Android test coverage

  120. Coverage 88%

  121. Demo https://github.com/filipmaelbrancke/devfest-istanbul-2014

  122. References

  123. Suggested reading Android Application Testing Guide Diego Torres Milano (9781849513500)

    Robotium Automated Testing for Android Hrushikesh Zadgaonkar (9781782168010) The Busy Coder’s Guide to Android Development Mark Murphy - http://commonsware.com/Android/
  124. Suggested reading Test Driven Development: By Example Beck, Kent (978-0321146533)

    Continuous Integration: Improving Software Quality and Reducing Risk Duvall, Paul M. et al. (978-0321336385) Working Effectively with Legacy Code Feathers, Michael (978-0131177055)
  125. Questions? Filip Maelbrancke Consultant @ AppFoundry filip.maelbrancke@appfoundry.be @fmaelbrancke