The real beginner's guide to Android testing

Easy to follow, contains only what's absolutely necessary to get started. Starts with MVP but expands to MVVM. Follow up Medium article on UI testing also available

Transcript

1. The real beginner’s guide to Android testing Eric Nguyen
2. About myself • Software Engineer at Grab • DragonBall fan (Vegeta fan) • @ericntd (LinkedIn, Medium, Github, StackoverFlow, Twitter) • Send me your resume eric.nguyen at grab.com - https://grab.careers/ #droidconvn
3. My journey with unit testing Before unit tests With unit tests #droidconvn @ericntd
4. Agenda 1. Why write tests 2. Types of tests 3. Introduction to unit testing 4. Challenge to unit testing with Android 5. The solution 6. Steps to your first Android unit tests 7. MVP architecture limitations 8. Q & A @ericntd
5. 1) Why write tests? • Improve and maintain product quality with less QA’s manual effort • Increase confidence when shipping • Perform routine exhaustive checks humans can’t perform, fast • Help you write more modular code @ericntd
6. 2) Different of type of tests Unit tests Component/ Integration Tests End-to- end tests 20-30 mins to run 100++ component UI tests <10 mins to run 4000 tests Fast to run, easy to write, run and to measure coverage Slow to run, difficult to write, run and to measure coverage #droidconvn @ericntd
7. 3) Unit testing crash course public class Calculator { /** * @param input an integer in the range of [Integer.MIN_VALUE/2, Integer.MAX_VALUE/2] * @return -1 if the input is too big or too small, otherwise the input times 2 */ public int timesTwo(int input) { if (input > Integer.MAX_VALUE / 2 || input < Integer.MIN_VALUE / 2) { return -1; } return input * 2; } } • • @ericntd
8. 3) Unit testing crash course dependencies { //... testImplementation 'junit:junit:4.12' testImplementation "org.mockito:mockito-core:2.12.0" } app/build.gradle #droidconvn public class CalculatorTest { private Calculator calculator = new Calculator(); @Test public void plusTwo() { Assert.assertEquals(0, calculator.timesTwo(0)); Assert.assertEquals(2, calculator.timesTwo(1)); } } app/src/test/java/your.package.name @ericntd
9. 3) Unit testing crash course public class CalculatorTest { private Calculator calculator = new Calculator(); @Test public void plusTwo() { Assert.assertEquals(0, calculator.timesTwo(0)); Assert.assertEquals(2, calculator.timesTwo(1)); Assert.assertEquals(-2, calculator.timesTwo(-1)); Assert.assertEquals(-1, calculator.timesTwo(Integer.MAX_VALUE)); Assert.assertEquals(-1, calculator.timesTwo(Integer.MIN_VALUE)); Assert.assertEquals(2147483646, calculator.timesTwo(Integer.MAX_VALUE / 2)); Assert.assertEquals(-1, calculator.timesTwo(Integer.MAX_VALUE / 2 + 1)); Assert.assertEquals(-2147483648, calculator.timesTwo(Integer.MIN_VALUE / 2)); Assert.assertEquals(-1, calculator.timesTwo(Integer.MIN_VALUE / 2 - 1)); } } @ericntd
10. 3) Unit testing crash course • @ericntd
11. 3) Unit testing crash course • @ericntd
12. 3) Unit testing crash course Unit tests also force us to write modular code The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long.” - Clean Code @ericntd
13. 4) Challenge of unit testing in Android • Consider a simple activity: ◦ A TextView display a number, starting from 1 ◦ A Button named “Time Two” • @ericntd
14. 4) Challenge of unit testing in Android public class CalculatorActivity extends AppCompatActivity { ` public Calculator calculator; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_calculator); calculator = new Calculator(); final TextView tvNumber = findViewById(R.id.tv_number); Button ctaTimesTwo = findViewById(R.id.cta_times_two); ctaTimesTwo.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { updateNumber(tvNumber); } }); } public void updateNumber(TextView tvNumber) { tvNumber.setText(calculator.timesTwo(Integer.valueOf(tvNumber.getText().toString()))); } } @ericntd
15. 4) Challenge of unit testing in Android public class CalculatorActivity extends AppCompatActivity { public Calculator calculator; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_calculator); calculator = new Calculator(); final TextView tvNumber = findViewById(R.id.tv_number); Button ctaTimesTwo = findViewById(R.id.cta_times_two); ctaTimesTwo.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { updateNumber(tvNumber); } }); } public void updateNumber(TextView tvNumber) { tvNumber.setText(calculator.timesTwo(Integer.valueOf(tvNumber.getText().toString()))); } } @ericntd
16. 4) Challenge of unit testing in Android public class CalculatorActivityTest { private CalculatorActivity activity = new CalculatorActivity(); @Test public void updateNumber() { // Preparation TextView tvNumber = Mockito.mock(TextView.class); Mockito.doReturn("1").when(tvNumber).getText(); // Trigger activity.updateNumber(tvNumber); // Validation Assert.assertEquals("2", tvNumber.getText().toString()); Mockito.verify(tvNumber).setText(2); } } • • @ericntd
17. 4) Challenge of unit testing in Android We run CalculatorActivityTest and we get a NullPointerException. @ericntd
18. 4) Challenge of unit testing in Android Possible Workarounds: • ◦ • ◦ @ericntd
19. 5) Solution for unit testing in Android • We need to move our business logics outside of the Activity or Fragment • We need to refactor our app from MVC to a better architecture such as Model-View-Presenter (MVP) @ericntd
20. 5) Solution for unit testing in Android - Architectures #droidconvn • Difficult to test logics within Activity/ Fragment • Activity/ Fragment are bloated Model-View-Presenter View (Fragment/ Activity) Presenter Activity/ Fragment Model-View-Controller Controller View • Business logics easily tested • Activity/ Fragment much thinner without business logics @ericntd
21. 6) Steps to your first Android unit tests A. Refactor your app to MVP B. Write tests for your Presenter (contains business logics) C. Profit! #droidconvn @ericntd
22. Sample app: GitHub Search https://github.com/ericntd/Github-Search @ericntd
23. A) MVC => MVP + #droidconvn public class MainActivity extends AppCompatActivity { //... private void searchGitHubRepos(GitHubApi gitHubApi, String query) { gitHubApi.searchRepos(query).enqueue(new Callback<SearchResponse>() { @Override public void onResponse(Call<SearchResponse> call, Response<SearchResponse> response) { handleResponse(response); } @Override public void onFailure(Call<SearchResponse> call, Throwable t) { handleError("E103 - System error"); } }); } } • • @ericntd
24. A) MVC => MVP public class SearchPresenter implements SearchPresenterContract, GitHubRepository .GitHubRepositoryCallback { private final SearchViewContract viewContract; private final GitHubRepository repository; //... @Override public void searchGitHubRepos(@Nullable final String query) { if (query != null && query.length() > 0) { repository.searchRepos(query, this); } } } • • @ericntd
25. A) MVC => MVP public class MainActivity extends AppCompatActivity implements SearchViewContract { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //... } @Override public void displaySearchResults(@NonNull List<SearchResult> searchResults, @Nullable Integer totalCount) { rvAdapter.updateResults(searchResults); tvStatus.setText(String.format(Locale.US, "Number of results: %d", totalCount)); } @Override public void displayError() { Toast.makeText(this, "some error happened", Toast.LENGTH_SHORT).show(); } @Override public void displayError(String s) { Toast.makeText(this, s, Toast.LENGTH_SHORT).show(); } } @ericntd
26. B) Write tests for Presenter - Setup package tech.ericntd.githubsearch.search; public class SearchPresenterTest { private SearchPresenter presenter; @Mock private GitHubRepository repository; @Mock private SearchViewContract viewContract; @Before public void setUp() throws Exception { MockitoAnnotations.initMocks(this);// required for the "@Mock" annotations // Make presenter a mock while using mock repository and viewContract created above presenter = Mockito.spy(new SearchPresenter(viewContract, repository)); } // The tests } dependencies { //... testImplementation 'junit:junit:4.12' testImplementation "org.mockito:mockito-core:2.12.0" } app/build.gradle app/src/test/java/ • #droidconvn @ericntd
27. B) Write test for Presenter - Example package tech.ericntd.githubsearch.search; public class SearchPresenterTest { @Test public void searchGitHubRepos() { String searchQuery = "some query"; // Trigger presenter.searchGitHubRepos(searchQuery); // Validation Mockito.verify(repository, Mockito.times(1)).searchRepos(searchQuery, presenter); } } package tech.ericntd.githubsearch.search; public class SearchPresenter implements SearchPresenterContract, GitHubRepository.GitHubRepositoryCallback { @Override public void searchGitHubRepos(@Nullable final String query) { if (query != null && query.length() > 0) { repository.searchRepos(query, this); } } } #droidconvn @ericntd
28. B) Write test for Presenter - Example package tech.ericntd.githubsearch.search; public class SearchPresenterTest { @Test public void searchGitHubRepos() { String searchQuery = "some query"; // Trigger presenter.searchGitHubRepos(searchQuery); // Validation Mockito.verify(repository, Mockito.times(1)).searchRepos(searchQuery, presenter); } } package tech.ericntd.githubsearch.search; public class SearchPresenter implements SearchPresenterContract, GitHubRepository.GitHubRepositoryCallback { @Override public void searchGitHubRepos(@Nullable final String query) { if (query != null && query.length() > 0) { repository.searchRepos(query, this); } } } #droidconvn @ericntd
29. B) Write test for Presenter - Example package tech.ericntd.githubsearch.search; public class SearchPresenterTest { @Test public void searchGitHubRepos() { String searchQuery = "some query"; // Trigger presenter.searchGitHubRepos(searchQuery); // Validation Mockito.verify(repository, Mockito.times(1)).searchRepos(searchQuery, presenter); } } package tech.ericntd.githubsearch.search; public class SearchPresenter implements SearchPresenterContract, GitHubRepository.GitHubRepositoryCallback { @Override public void searchGitHubRepos(@Nullable final String query) { if (query != null && query.length() > 0) { repository.searchRepos(query, this); } } } #droidconvn @ericntd
30. B) Write test for Presenter - Example package tech.ericntd.githubsearch.search; public class SearchPresenterTest { @Test public void searchGitHubRepos() { String searchQuery = "some query"; // Trigger presenter.searchGitHubRepos(searchQuery); // Validation Mockito.verify(repository, Mockito.times(1)).searchRepos(searchQuery, presenter); } } package tech.ericntd.githubsearch.search; public class SearchPresenter implements SearchPresenterContract, GitHubRepository.GitHubRepositoryCallback { @Override public void searchGitHubRepos(@Nullable final String query) { if (query != null && query.length() > 0) { repository.searchRepos(query, this); } } } app/src/test/java/ app/src/main/java/ #droidconvn @ericntd
31. C) Run test & Profit! #droidconvn @ericntd
32. C) Run test & Profit! package tech.ericntd.githubsearch.search; public class SearchPresenterTest { @Test public void searchGitHubRepos_noQuery() { String searchQuery = null; // Trigger presenter.searchGitHubRepos(searchQuery); // Validation Mockito.verify(repository, Mockito.never()).searchRepos(searchQuery, presenter); } } package tech.ericntd.githubsearch.search; public class SearchPresenter implements SearchPresenterContract, GitHubRepository.GitHubRepositoryCallback { @Override public void searchGitHubRepos(@Nullable final String query) { if (query != null && query.length() > 0) { repository.searchRepos(query, this); } } } @ericntd
33. C) Run test & Profit! @Test public void handleGitHubResponse_Failure() { Response response = Mockito.mock(Response.class); Mockito.doReturn(false).when(response).isSuccessful(); // Trigger presenter.handleGitHubResponse(response); // Validation Mockito.verify(viewContract, Mockito.times(1)).displayError("E101 - System error"); } @ericntd @Test public void handleGitHubResponse_EmptyResponse() { Response response = Mockito.mock(Response.class); Mockito.doReturn(true).when(response).isSuccessful(); Mockito.doReturn(null).when(response).body(); // Trigger presenter.handleGitHubResponse(response); // Validation Mockito.verify(viewContract, Mockito.times(1)).displayError("E102 - System error"); }
34. C) Run test & Profit! @ericntd
35. @ericntd
36. 7) MVP architecture limitations public class MainActivity extends AppCompatActivity implements SearchViewContract { // ... @Override public void displaySearchResults(@NonNull List<SearchResult> searchResults, @Nullable Integer totalCount) { rvAdapter.updateResults(searchResults); tvStatus.setText(String.format(Locale.US, "Number of results: %d", totalCount)); } } #droidconvn @ericntd
37. 7) MVP architecture limitations • • • • • ⇒ #droidconvn @ericntd
38. 7) MVP architecture limitations Introducing Model-View-ViewModel Model-View-ViewModel View (.xml layout) ViewModel Data Binding @ericntd
39. 7) MVP architecture limitations // no more logic here MainActivity <?xml version="1.0" encoding="utf-8"?> <layout > <data> <variable name="vm" type="tech.ericntd.githubsearch.search.SearchViewModel" /> </data> <android.support.constraint.ConstraintLayout> <TextView android:id="@+id/tv_status" android:layout_width="match_parent" android:layout_height="wrap_content" android:paddingEnd="16dp" android:paddingStart="16dp" android:text="@{vm.status}" app:layout_constraintTop_toBottomOf="@id/et_search_query" tools:text="Number of results: 1000000" /> </android.support.constraint.ConstraintLayout> </layout> activity_main.xml @ericntd
40. 7) MVP architecture limitations public class SearchViewModel implements GitHubRepository .GitHubRepositoryCallback { public ObservableField<String> status = new ObservableField<>(); @Override public void handleGitHubResponse(@NonNull final Response<SearchResponse> response) { if (response.isSuccessful()) { SearchResponse searchResponse = response.body(); if (searchResponse != null && searchResponse.getSearchResults() != null) { renderSuccess(searchResponse); } } } private void renderSuccess(SearchResponse searchResponse) { status.set(String.format(Locale.US, "Number of results: %d", searchResponse .getTotalCount())); } } SearchViewModel public class SearchViewModelTest { @Test public void renderSuccess() { Response response = Mockito.mock(Response.class); SearchResponse searchResponse = Mockito.mock(SearchResponse.class); Mockito.doReturn(true).when(response).isSuccessful(); Mockito.doReturn(searchResponse).when(response).body(); Mockito.doReturn(1001).when(searchResponse).getTotalCount(); // Trigger viewModel.handleGitHubResponse(response); // Validation Assert.assertEquals("Number of results: 1001", viewModel.status.get()); } } SearchViewModelTest @ericntd
41. 7) MVP architecture limitations • Notes on MVVM ◦ Your XML layout is not tested, so avoid complex logic #droidconvn @ericntd
42. Takeaways Architecture your app for testing
43. Android testing articles series Part 1: A beginner’s guide to automated (unit) testing (today’s talk) Part 2: Better tests with MVVM + data binding Part 3: Component UI tests with Espresso from 0 to 1 #droidconvn @ericntd
44. References https://github.com/googlesamples/android-architecture https://codelabs.developers.google.com/codelabs/android-testing/#0 #droidconvn @ericntd
45. Q & A #droidconvn @ericntd
46. Thank you @ericntd • @ericntd (LinkedIn, Medium, Github, StackoverFlow, Twitter) • Send me your resume eric.nguyen at grab.com - https://grab.careers/