Unit Testing in a Nutshell Fumihiko Shiroyama DroidKaigi 2018

Who is this guy? • Senior Android Developer @nikkei • Executive Beer Drinker • Chief Baby Sitter at home • Unit Test Enthusiast

Agenda today • Why you should care about Unit Testing • JUnit4 and basic assertions • Mock and spy with Mockito • Robolectric for framework's code • Unit Testing SQLite • Unit Testing asynchronous code • Best practices and tips

Why you should care about Unit Testing?

What if you DON'T?

public class LoginActivity extends AppCompatActivity implements LoaderCallbacks { private static final int REQUEST_READ_CONTACTS = 0; private static final String[] DUMMY_CREDENTIALS = new String[]{ "[email protected]:hello", "[email protected]:world" }; private UserLoginTask mAuthTask = null; private AutoCompleteTextView mEmailView; private EditText mPasswordView; private View mProgressView; private View mLoginFormView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_login); mEmailView = (AutoCompleteTextView) findViewById(R.id.email); populateAutoComplete(); mPasswordView = (EditText) findViewById(R.id.password); mPasswordView.setOnEditorActionListener(new TextView.OnEditorActionListener() { @Override public boolean onEditorAction(TextView textView, int id, KeyEvent keyEvent) { if (id == EditorInfo.IME_ACTION_DONE || id == EditorInfo.IME_NULL) { attemptLogin(); return true; } return false; } }); Button mEmailSignInButton = (Button) findViewById(R.id.email_sign_in_button); mEmailSignInButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View view) { attemptLogin(); } }); mLoginFormView = findViewById(R.id.login_form); mProgressView = findViewById(R.id.login_progress); } private void populateAutoComplete() { if (!mayRequestContacts()) { return; } getLoaderManager().initLoader(0, null, this); } private boolean mayRequestContacts() { if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) { return true; } if (checkSelfPermission(READ_CONTACTS) == PackageManager.PERMISSION_GRANTED) { return true; } if (shouldShowRequestPermissionRationale(READ_CONTACTS)) { Snackbar.make(mEmailView, R.string.permission_rationale, Snackbar.LENGTH_INDEFINITE) .setAction(android.R.string.ok, new View.OnClickListener() { @Override @TargetApi(Build.VERSION_CODES.M) public void onClick(View v) { requestPermissions(new String[]{READ_CONTACTS}, REQUEST_READ_CONTACTS); } }); } else { requestPermissions(new String[]{READ_CONTACTS}, REQUEST_READ_CONTACTS); } return false; } @Override public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { if (requestCode == REQUEST_READ_CONTACTS) { if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { populateAutoComplete(); } } } private void attemptLogin() { if (mAuthTask != null) { return; } mEmailView.setError(null); mPasswordView.setError(null); String email = mEmailView.getText().toString(); String password = mPasswordView.getText().toString(); boolean cancel = false; View focusView = null; if (!TextUtils.isEmpty(password) && !isPasswordValid(password)) { mPasswordView.setError(getString(R.string.error_invalid_password)); focusView = mPasswordView; cancel = true; } if (TextUtils.isEmpty(email)) { mEmailView.setError(getString(R.string.error_field_required)); focusView = mEmailView; cancel = true; } else if (!isEmailValid(email)) { mEmailView.setError(getString(R.string.error_invalid_email)); focusView = mEmailView; cancel = true; } if (cancel) { focusView.requestFocus(); } else { showProgress(true); mAuthTask = new UserLoginTask(email, password); mAuthTask.execute((Void) null); } }

public class LoginActivity extends AppCompatActivity implements LoaderCallbacks { private static final int REQUEST_READ_CONTACTS = 0; private static final String[] DUMMY_CREDENTIALS = new String[]{ "[email protected]:hello", "[email protected]:world" }; private UserLoginTask mAuthTask = null; private AutoCompleteTextView mEmailView; private EditText mPasswordView; private View mProgressView; private View mLoginFormView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_login); mEmailView = (AutoCompleteTextView) findViewById(R.id.email); populateAutoComplete(); mPasswordView = (EditText) findViewById(R.id.password); mPasswordView.setOnEditorActionListener(new TextView.OnEditorActionListener() { @Override public boolean onEditorAction(TextView textView, int id, KeyEvent keyEvent) { if (id == EditorInfo.IME_ACTION_DONE || id == EditorInfo.IME_NULL) { attemptLogin(); return true; } return false; } }); Button mEmailSignInButton = (Button) findViewById(R.id.email_sign_in_button); mEmailSignInButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View view) { attemptLogin(); } }); mLoginFormView = findViewById(R.id.login_form); mProgressView = findViewById(R.id.login_progress); } private void populateAutoComplete() { if (!mayRequestContacts()) { return; } getLoaderManager().initLoader(0, null, this); } private boolean mayRequestContacts() { if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) { return true; } if (checkSelfPermission(READ_CONTACTS) == PackageManager.PERMISSION_GRANTED) { return true; } if (shouldShowRequestPermissionRationale(READ_CONTACTS)) { Snackbar.make(mEmailView, R.string.permission_rationale, Snackbar.LENGTH_INDEFINITE) .setAction(android.R.string.ok, new View.OnClickListener() { @Override @TargetApi(Build.VERSION_CODES.M) public void onClick(View v) { requestPermissions(new String[]{READ_CONTACTS}, REQUEST_READ_CONTACTS); } }); } else { requestPermissions(new String[]{READ_CONTACTS}, REQUEST_READ_CONTACTS); } return false; } @Override public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { if (requestCode == REQUEST_READ_CONTACTS) { if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { populateAutoComplete(); } } } private void attemptLogin() { if (mAuthTask != null) { return; } mEmailView.setError(null); mPasswordView.setError(null); String email = mEmailView.getText().toString(); String password = mPasswordView.getText().toString(); boolean cancel = false; View focusView = null; if (!TextUtils.isEmpty(password) && !isPasswordValid(password)) { mPasswordView.setError(getString(R.string.error_invalid_password)); focusView = mPasswordView; cancel = true; } if (TextUtils.isEmpty(email)) { mEmailView.setError(getString(R.string.error_field_required)); focusView = mEmailView; cancel = true; } else if (!isEmailValid(email)) { mEmailView.setError(getString(R.string.error_invalid_email)); focusView = mEmailView; cancel = true; } if (cancel) { focusView.requestFocus(); } else { showProgress(true); mAuthTask = new UserLoginTask(email, password); mAuthTask.execute((Void) null); } } Faaaaaaaaaaaat Controller!!

Fat Controller is bad because... • Slow iteration • Ambiguous responsibilities • Off-by-one errors • Un-reproducible bugs

Unit testing lets you... • Faster execution • Clear division of roles • Chance to improve architecture

Is unit testing just enough?

No!! It just ensures it partially worked

See also... • EspressoςετίʔυͷಉظॲཧΛڀΊΔ • Day1 Room5 15:40 - • UIςετͷ࣮ߦ࣌ؒΛ୹ॖͤ͞Δํ๏ • Day2 Room2 18:30 -

anyway

JUnit4 and basic assertions

JUnit4 is... • A simple testing framework • Available for Android out-of-the-box • Still de-facto standard Moving Forward with JUnit 5 - Day2 Room5 10:30 - Check also

Assertions

Assertion is... • Assert something is something A rose is a rose is a rose is a rose... assertThat(1 + 1).isEqualTo(2); assertThat("Alice") .isNotEmpty() .isNotEqualTo("Bob");

Installation dependencies { testImplementation 'junit:junit:4.12' testImplementation 'com.squareup.assertj:assertj-android:1.2.0' } assertj-android lets you assert Android framework's code as well

Test target class InputChecker { boolean isValid(String text) { if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; } } VERY SIMPLE input text checker

Create New Test Command + SHIFT + T

Create New Test

Create New Test

Types of test in Android • Local Unit Tests • Runs on JVM • src/test • Instrumented Tests • Runs with Device/Emulators • src/androidTest

Local Unit Tests: pros • Runs fast! • No device, emulator, android sdk

Local Unit Tests: cons • No REAL Android framework's code

• TRUE Android Test • Exactly the same behavior as production Instrumented Tests: pros

Instrumented Tests: cons • Runs slow! • Need device, emulator, android sdk

This session only cares Local Unit Tests

Test class public class InputCheckerTest { @Before public void setUp() throws Exception { } @Test public void isValid() throws Exception { } }

Test class public class InputCheckerTest { @Before public void setUp() throws Exception { } @Test public void isValid() throws Exception { } } Just naming convention

Test class public class InputCheckerTest { @Before public void setUp() throws Exception { } @Test public void isValid() throws Exception { } } Called at every test case

Test class public class InputCheckerTest { @Before public void setUp() throws Exception { } @Test public void isValid() throws Exception { } } This is a test case Write as many as you want

Test class public class InputCheckerTest { @Before public void setUp() throws Exception { }foo @Test public void isValid() throws Exception { }foo }foo

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); }foo @Test public void isValid() throws Exception { }foo }foo

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test public void isValid() throws Exception { } } Initialization codes here

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); }foo @Test public void isValid() throws Exception { }foo }foo

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); }foo @Test public void isValid() throws Exception { String input = "voodoo"; boolean actual = inputChecker.isValid(input); Assertions.assertThat(actual).isTrue(); }foo }foo

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test public void isValid() throws Exception { String input = "voodoo"; boolean actual = inputChecker.isValid(input); Assertions.assertThat(actual).isTrue(); } } Write your assertions

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test public void isValid() throws Exception { String input = "voodoo"; boolean actual = inputChecker.isValid(input); Assertions.assertThat(actual).isTrue(); } } what really is "actual"

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test public void isValid() throws Exception { String input = "voodoo"; boolean actual = inputChecker.isValid(input); Assertions.assertThat(actual).isTrue(); } } "expectation" what you expect it to be

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test public void isValid() throws Exception { String input = "voodoo"; boolean actual = inputChecker.isValid(input); Assertions.assertThat(actual).isTrue(); } } From AssertJ Many assertion methods available

Test class public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test public void isValid() throws Exception { String input = "voodoo"; boolean actual = inputChecker.isValid(input); Assertions.assertThat(actual).isTrue(); } }

Run tests Run single Run all or Passed!!!!

If it fails... reason why it failed failure... Fix and try again!!!

Congrats!!!

Assertions (AssertJ) • assertThat(all) • isEqualTo / isNotEqualTo • assertThat(String) • isEmpty / isNotEmpty • assertThat(Number) • isPositive / isNegative / isZero / isNotZero • isGreaterThan / isLessThan lots and lots and lots more

• assertThat(list) • contains / containsOnly / containsExactly Assertions (AssertJ) lots and lots and lots more List strings = Arrays.asList("foo", "bar", "baz"); assertThat(strings).contains("bar"); same collection same collection and order

• http://joel-costigliola.github.io/assertj/ • https://github.com/square/assertj-android • https://qiita.com/opengl-8080/items/ b07307ab0d33422be9c5 AssertJ

Exceptions

Remember this... class InputChecker { boolean isValid(String text) { if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; } }

Remember this... class InputChecker { boolean isValid(String text) { if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; } } What if null... Let's try it anyway

Ouch!! @Test public void isValid() throws Exception { String input = null; boolean actual = inputChecker.isValid(input); assertThat(actual).isTrue(); }

Expected Exception @Test(expected = NullPointerException.class) public void isValid() throws Exception { String input = null; boolean actual = inputChecker.isValid(input); assertThat(actual).isTrue(); }

Expected Exception @Test(expected = NullPointerException.class) public void isValid() throws Exception { String input = null; boolean actual = inputChecker.isValid(input); assertThat(actual).isTrue(); }

Passed!! @Test(expected = NullPointerException.class) public void isValid() throws Exception { String input = null; boolean actual = inputChecker.isValid(input); assertThat(actual).isTrue(); }

Better yet... class InputChecker { boolean isValid(String text) { if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; }foo }foo

Better yet... class InputChecker { boolean isValid(@NonNull String text) { if (text == null) throw new IllegalArgumentException("cannot be null"); if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; }foo }foo

Better yet... class InputChecker { boolean isValid(@NonNull String text) { if (text == null) throw new IllegalArgumentException("cannot be null"); if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; } }

Better yet... class InputChecker { boolean isValid(@NonNull String text) { if (text == null) throw new IllegalArgumentException("cannot be null"); if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; } } Unit testing helps you refactoring!!

Way better!! @Test(expected = IllegalArgumentException.class) public void isValid() throws Exception { String input = null; boolean actual = inputChecker.isValid(input); assertThat(actual).isTrue(); }

Mock and spy with Mockito

Mock is... • A WHOLE imitation of a real object • Used to simulate the behavior of depending objects

Spy is... • A PARTIAL imitation of a real object • Used to simulate the behavior of depending objects

Test Doubles They are

Why you need mocks?

TweetRepository public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository(LocalTweetDataSource localDataSource) { this.localDataSource = localDataSource; } public List getTimeline() { return localDataSource.getTimeline(); } }

TweetRepository public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository(LocalTweetDataSource localDataSource) { this.localDataSource = localDataSource; } public List getTimeline() { return localDataSource.getTimeline(); } } depending on local data source

Data Source public class LocalTweetDataSource { public List getTimeline() { List tweets = new ArrayList<>(); // some local DB interaction // ..... return tweets; } }

Data Source public class LocalTweetDataSource { public List getTimeline() { List tweets = new ArrayList<>(); // some local DB interaction // ..... return tweets; } } Because it dose so many interactions with DB You don't wanna deal with all those messes!

TweetRepository public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository(LocalTweetDataSource localDataSource) { this.localDataSource = localDataSource; } public List getTimeline() { return localDataSource.getTimeline(); } } You can replace this with simple mock

Mockito

Mockito is... • A simple mocking library • Most used one in Java and Android community

Installation dependencies { testImplementation 'org.mockito:mockito-inline:2.13.0' } mockito-inline lets you mock final class & methods this artifact may be integrated into default in the future but you can't mock static methods & constructors

Stubbing

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) );

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) );

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) );

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) ); mock instance

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn(); stub method

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn();

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn();

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn();

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( );zz

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) );zz

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) );zz any item you wanna return

Stubbing import static org.mockito.Mockito.*; LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) );

Stubbing private TweetRepository tweetRepository; @Before public void setUp() throws Exception { LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) ); tweetRepository = new TweetRepository(localDataSource); }

Stubbing private TweetRepository tweetRepository; @Before public void setUp() throws Exception { LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ) ); tweetRepository = new TweetRepository(localDataSource); }

Stubbing @Test public void getTimeline() throws Exception { List tweets = tweetRepository.getTimeline(); assertThat(tweets) .isNotEmpty() .hasSize(3) .containsExactly( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ); }

Stubbing @Test public void getTimeline() throws Exception { List tweets = tweetRepository.getTimeline(); assertThat(tweets) .isNotEmpty() .hasSize(3) .containsExactly( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ); }

Stubbing @Test public void getTimeline() throws Exception { List tweets = tweetRepository.getTimeline(); assertThat(tweets) .isNotEmpty() .hasSize(3) .containsExactly( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ); }

Stubbing @Test public void getTimeline() throws Exception { List tweets = tweetRepository.getTimeline(); assertThat(tweets) .isNotEmpty() .hasSize(3) .containsExactly( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ); }

Stubbing @Test public void getTimeline() throws Exception { List tweets = tweetRepository.getTimeline(); assertThat(tweets) .isNotEmpty() .hasSize(3) .containsExactly( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz") ); } pass!!

Spying

Spying is... • Stub methods can be added on a REAL object That means spied objects acts EXACTLY the same as real objects unless stubbed

Spying List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) ); verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Spying List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) ); verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt()); normal ArrayList

Spying List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) ); verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt()); wrap with spy()

Spying List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) ); verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt()); things you typically to with List

Verify • Check the interactions with mock/spy mocks/spies will remember all interactions

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify( );abc verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) );abc verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) );abc verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) );abc verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) );abc verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) );abc verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) );abc verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt()); notice!

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) );abc verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) ); verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt());

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) ); verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt()); no interaction

Verify List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); verify(strings, times(1)).addAll( eq(Arrays.asList("pop", "team", "epic")) ); verify(strings, never()).add(eq("pop")); verify(strings, never()).get(anyInt()); argument matcher

Argument matchers • eq(T) • anyString() • anyInt() • any() • any(Class) • nullable(Class) null or T including null

Stubbing with callbacks List strings = spy(new ArrayList()); String[] array = {"pop", "team", "epic"}; strings.addAll(asList(array)); when(strings.get(anyInt())).thenAnswer(invocation -> { Object[] arguments = invocation.getArguments(); int index = (int) arguments[0]; if (index < array.length) return array[index]; return "something-else"; }); String got = strings.get(123); assertThat(got).isEqualTo("something-else"); if you wanna change return val according to the arguments

Stubbing with callbacks List strings = spy(new ArrayList()); String[] array = {"pop", "team", "epic"}; strings.addAll(asList(array)); when().thenAnswer(invocation -> { });

Stubbing with callbacks List strings = spy(new ArrayList()); String[] array = {"pop", "team", "epic"}; strings.addAll(asList(array)); when(strings.get(anyInt())).thenAnswer(invocation -> { Object[] arguments = invocation.getArguments(); int index = (int) arguments[0]; if (index < array.length) return array[index]; return "something-else"; }); String got = strings.get(123); assertThat(got).isEqualTo("something-else");

Stubbing with callbacks List strings = spy(new ArrayList()); String[] array = {"pop", "team", "epic"}; strings.addAll(asList(array)); when(strings.get(anyInt())).thenAnswer(invocation -> { Object[] arguments = invocation.getArguments(); int index = (int) arguments[0]; if (index < array.length) return array[index]; return "something-else"; }); String got = strings.get(123); assertThat(got).isEqualTo("something-else");

Stubbing with callbacks List strings = spy(new ArrayList()); String[] array = {"pop", "team", "epic"}; strings.addAll(asList(array)); when(strings.get(anyInt())).thenAnswer(invocation -> { Object[] arguments = invocation.getArguments(); int index = (int) arguments[0]; if (index < array.length) return array[index]; return "something-else"; }); String got = strings.get(123); assertThat(got).isEqualTo("something-else");

Stubbing with callbacks List strings = spy(new ArrayList()); String[] array = {"pop", "team", "epic"}; strings.addAll(asList(array)); when(strings.get(anyInt())).thenAnswer(invocation -> { Object[] arguments = invocation.getArguments(); int index = (int) arguments[0]; if (index < array.length) return array[index]; return "something-else"; }); String got = strings.get(123); assertThat(got).isEqualTo("something-else"); whatever logic you like

Stubbing with callbacks List strings = spy(new ArrayList()); String[] array = {"pop", "team", "epic"}; strings.addAll(asList(array)); when(strings.get(anyInt())).thenAnswer(invocation -> { Object[] arguments = invocation.getArguments(); int index = (int) arguments[0]; if (index < array.length) return array[index]; return "something-else"; }); String got = strings.get(123); assertThat(got).isEqualTo("something-else"); Don't abuse this since it spoils simplicity

Stubbing spy method

doReturn List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); when(strings.get(3)).thenReturn("foo"); when().thenReturn() is almost always useful

doReturn List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); when(strings.get(3)).thenReturn("foo"); 0 1 2 Because this is a spy, not mock, List#get() is evaluated first that causes an Exception

doReturn List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); doReturn("foo").when(strings).get(3); String got = strings.get(3); Assertions.assertThat(got).isEqualTo("foo");

doReturn List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); doReturn("foo").when(strings).get(3); String got = strings.get(3); Assertions.assertThat(got).isEqualTo("foo");

doReturn List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); doReturn("foo").when(strings).get(3); String got = strings.get(3); Assertions.assertThat(got).isEqualTo("foo");

doReturn List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); doReturn("foo").when(strings).get(3); String got = strings.get(3); Assertions.assertThat(got).isEqualTo("foo");

doReturn List strings = spy(new ArrayList()); strings.addAll(Arrays.asList("pop", "team", "epic")); strings.forEach(System.out::println); doReturn("foo").when(strings).get(3); String got = strings.get(3); Assertions.assertThat(got).isEqualTo("foo"); This works well!

Stubbing void method

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); strings.clear();

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); strings.clear();

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); strings.clear();

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); strings.clear();

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); strings.clear();

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); strings.clear();

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); doNothing().when(strings).clear(); strings.clear();

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); doNothing().when(strings).clear(); strings.clear();

doThrow / doNothing List strings = spy(new ArrayList()); doThrow(new IllegalStateException()).when(strings).clear(); doNothing().when(strings).clear(); strings.clear(); pass!!

• http://site.mockito.org/ • http://static.javadoc.io/org.mockito/mockito-core/ 2.13.0/org/mockito/Mockito.html#0 Mockito REALLY HELPFUL!!

Robolectric for framework's code

InputChecker class InputChecker { boolean isValid(@NonNull String text) { if (text == null) throw new IllegalArgumentException("cannot be null"); if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; } }

InputChecker class InputChecker { boolean isValid(@NonNull String text) { if (TextUtils.isEmpty(text)) throw new IllegalArgumentException("cannot be blank"); if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; } }

InputChecker class InputChecker { boolean isValid(@NonNull String text) { if (TextUtils.isEmpty(text)) throw new IllegalArgumentException("cannot be blank"); if (text.length() < 4) return false; if (!text.matches("[a-zA-Z0-9]+")) return false; return true; } } android.text.TextUtils

InputCheckerTest public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test public void isValid() throws Exception { String input = "voodoo"; boolean actual = inputChecker.isValid(input); assertThat(actual).isTrue(); } }

InputCheckerTest Basically, Android framework's code cannot be executed on JVM tests

app/build.gradle android { testOptions { unitTests.returnDefaultValues = true } } notice: this setting just return the default value @Test isValid() passes successfully

InputCheckerTest public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test(expected = IllegalArgumentException.class) public void isValid_fails_with_blank() throws Exception { String input = ""; inputChecker.isValid(input); } } Add a test case that checks blank input

InputCheckerTest public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test(expected = IllegalArgumentException.class) public void isValid_fails_with_blank() throws Exception { String input = ""; inputChecker.isValid(input); } } Expected exception was not thrown! This is because of the "default value" from test options

Robolectric

Robolectric is... • "A unit test framework that de-fangs the Android SDK jar so you can test-drive the development of your Android app." • "Tests run inside the JVM on your workstation in seconds." quoted from the official site

testImplementation "org.robolectric:robolectric:3.6.1" android { testOptions { unitTests { includeAndroidResources = true } } } Installation remove: unitTests.returnDefaultValues = true

InputCheckerTest @RunWith(RobolectricTestRunner.class) public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test(expected = IllegalArgumentException.class) public void isValid_fails_with_blank() throws Exception { String input = ""; inputChecker.isValid(input); } }

InputCheckerTest @RunWith(RobolectricTestRunner.class) public class InputCheckerTest { private InputChecker inputChecker; @Before public void setUp() throws Exception { inputChecker = new InputChecker(); } @Test(expected = IllegalArgumentException.class) public void isValid_fails_with_blank() throws Exception { String input = ""; inputChecker.isValid(input); } } Just add this!!

Context in Robolectric @RunWith(RobolectricTestRunner.class) public class SQLiteTest { private SQLiteDatabase db; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); SQLiteOpenHelper helper = new MySQLiteOpenHelper(context); db = helper.getWritableDatabase(); } @Test public void test_db() throws Exception { // do the stuff } }

Context in Robolectric @RunWith(RobolectricTestRunner.class) public class SQLiteTest { private SQLiteDatabase db; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); SQLiteOpenHelper helper = new MySQLiteOpenHelper(context); db = helper.getWritableDatabase(); } @Test public void test_db() throws Exception { // do the stuff } } Really handy to use!!

• http://robolectric.org/ • http://robolectric.org/getting-started/ • http://robolectric.org/extending/ Robolectric One thing you have to notice about Robolectric is It just mimics the framework's behavior, not the real one

Unit Testing SQLite

• Robolectric simulates SQLite out-of-the-box!! • You can use traditional SQLiteOpenHelper • You can also use the latest Room Persistence Library Unit Testing SQLite

Room Persistence Library dependencies { implementation "android.arch.persistence.room:runtime:1.0.0" annotationProcessor "android.arch.persistence.room:compiler:1.0.0" }

Room Persistence Library @Entity public class User { @PrimaryKey private int uid; @ColumnInfo(name = "first_name") private String firstName; @ColumnInfo(name = "last_name") private String lastName; public User(String firstName, String lastName) { this.firstName = firstName; this.lastName = lastName; } // getters & setters } Entity

Room Persistence Library @Dao public interface UserDao { @Query("SELECT * FROM user") List getAll(); @Query("SELECT * FROM user WHERE uid IN (:userIds)") List loadAllByIds(int[] userIds); @Query("SELECT * FROM user WHERE first_name LIKE :first AND " + "last_name LIKE :last LIMIT 1") User findByName(String first, String last); @Insert void insertAll(User... users); @Delete void delete(User user); } Dao

Room Persistence Library @Database(entities = {User.class}, version = 1) public abstract class AppDatabase extends RoomDatabase { public abstract UserDao userDao(); } Database

Room Persistence Library public class UserManager { private final String DB_NAME = "sample_app"; private final AppDatabase db; public UserManager(@NonNull Context context) { db = Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class, DB_NAME) .allowMainThreadQueries() .build(); } public void insertUser(@NonNull User user) { db.userDao().insertAll(user); } public List getUsers() { return db.userDao().getAll(); } } Business Logic

Room Persistence Library public class UserManager { private final String DB_NAME = "sample_app"; private final AppDatabase db; public UserManager(@NonNull Context context) { db = Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class, DB_NAME) .allowMainThreadQueries() .build(); } public void insertUser(@NonNull User user) { db.userDao().insertAll(user); } public List getUsers() { return db.userDao().getAll(); } } Business Logic just for demo's convenience

Room Persistence Library public class UserManager { private final String DB_NAME = "sample_app"; private final AppDatabase db; public UserManager(@NonNull Context context) { db = Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class, DB_NAME) .allowMainThreadQueries() .build(); } public void insertUser(@NonNull User user) { db.userDao().insertAll(user); } public List getUsers() { return db.userDao().getAll(); } } Business Logic delegate

Room Persistence Library public class UserManager { private final String DB_NAME = "sample_app"; private final AppDatabase db; public UserManager(@NonNull Context context) { db = Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class, DB_NAME) .allowMainThreadQueries() .build(); } public void insertUser(@NonNull User user) { db.userDao().insertAll(user); } public List getUsers() { return db.userDao().getAll(); } } Business Logic delegate

Room Persistence Library @RunWith(RobolectricTestRunner.class) public class UserManagerTest { private UserManager userManager; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); userManager = new UserManager(context); } @Test public void insert_and_get() throws Exception { List users = userManager.getUsers(); assertThat(users).isEmpty(); userManager.insertUser(new User("Fumihiko", "Shiroyama")); users = userManager.getUsers(); assertThat(users) .isNotEmpty() .hasSize(1); } }

Room Persistence Library @RunWith(RobolectricTestRunner.class) public class UserManagerTest { private UserManager userManager; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); userManager = new UserManager(context); } @Test public void insert_and_get() throws Exception { List users = userManager.getUsers(); assertThat(users).isEmpty(); userManager.insertUser(new User("Fumihiko", "Shiroyama")); users = userManager.getUsers(); assertThat(users) .isNotEmpty() .hasSize(1); } }

Room Persistence Library @RunWith(RobolectricTestRunner.class) public class UserManagerTest { private UserManager userManager; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); userManager = new UserManager(context); } @Test public void insert_and_get() throws Exception { List users = userManager.getUsers(); assertThat(users).isEmpty(); userManager.insertUser(new User("Fumihiko", "Shiroyama")); users = userManager.getUsers(); assertThat(users) .isNotEmpty() .hasSize(1); } }

Room Persistence Library @RunWith(RobolectricTestRunner.class) public class UserManagerTest { private UserManager userManager; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); userManager = new UserManager(context); } @Test public void insert_and_get() throws Exception { List users = userManager.getUsers(); assertThat(users).isEmpty(); userManager.insertUser(new User("Fumihiko", "Shiroyama")); users = userManager.getUsers(); assertThat(users) .isNotEmpty() .hasSize(1); } }

Room Persistence Library @RunWith(RobolectricTestRunner.class) public class UserManagerTest { private UserManager userManager; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); userManager = new UserManager(context); } @Test public void insert_and_get() throws Exception { List users = userManager.getUsers(); assertThat(users).isEmpty(); userManager.insertUser(new User("Fumihiko", "Shiroyama")); users = userManager.getUsers(); assertThat(users) .isNotEmpty() .hasSize(1); } }

Room Persistence Library @RunWith(RobolectricTestRunner.class) public class UserManagerTest { private UserManager userManager; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); userManager = new UserManager(context); } @Test public void insert_and_get() throws Exception { List users = userManager.getUsers(); assertThat(users).isEmpty(); userManager.insertUser(new User("Fumihiko", "Shiroyama")); users = userManager.getUsers(); assertThat(users) .isNotEmpty() .hasSize(1); } }

Room Persistence Library @RunWith(RobolectricTestRunner.class) public class UserManagerTest { private UserManager userManager; @Before public void setUp() throws Exception { Context context = RuntimeEnvironment.application.getApplicationContext(); userManager = new UserManager(context); } @Test public void insert_and_get() throws Exception { List users = userManager.getUsers(); assertThat(users).isEmpty(); userManager.insertUser(new User("Fumihiko", "Shiroyama")); users = userManager.getUsers(); assertThat(users) .isNotEmpty() .hasSize(1); } } DB & table's data are reset automatically

Room Persistence Library • https://developer.android.com/topic/ libraries/architecture/room.html • https://developer.android.com/topic/ libraries/architecture/adding- components.html • https://developer.android.com/training/ data-storage/room/index.html

Unit Testing asynchronous code

Testing async code • Testing asynchronous code is not always easy I'd introduce the very basic concept of it!

Synchronous call interface Fetcher { T fetch(); class StringFetcher implements Fetcher { @Override public String fetch() { return "OK"; } } } Think of a synchronous API call over internet

Simple callback Callback interfaces interface OnSuccess { void onSuccess(T result); } interface OnFailure { void onFailure(Exception e); }

Asynchronous call class AsyncFetcher { private final Fetcher fetcher; AsyncFetcher(Fetcher fetcher) { this.fetcher = fetcher; } void fetch(OnSuccess onSuccess, OnFailure onFailure) { new Thread(() -> { try { Thread.sleep(1000L); onSuccess.onSuccess(fetcher.fetch()); } catch (Exception e) { onFailure.onFailure(e); } }).start(); } } Think of an asynchronous API call over internet

Asynchronous call class AsyncFetcher { private final Fetcher fetcher; AsyncFetcher(Fetcher fetcher) { this.fetcher = fetcher; } void fetch(OnSuccess onSuccess, OnFailure onFailure) { new Thread(() -> { try { Thread.sleep(1000L); onSuccess.onSuccess(fetcher.fetch()); } catch (Exception e) { onFailure.onFailure(e); } }).start(); } }

Asynchronous call class AsyncFetcher { private final Fetcher fetcher; AsyncFetcher(Fetcher fetcher) { this.fetcher = fetcher; } void fetch(OnSuccess onSuccess, OnFailure onFailure) { new Thread(() -> { try { Thread.sleep(1000L); onSuccess.onSuccess(fetcher.fetch()); } catch (Exception e) { onFailure.onFailure(e); } }).start(); } }

Asynchronous call class AsyncFetcher { private final Fetcher fetcher; AsyncFetcher(Fetcher fetcher) { this.fetcher = fetcher; } void fetch(OnSuccess onSuccess, OnFailure onFailure) { new Thread(() -> { try { Thread.sleep(1000L); onSuccess.onSuccess(fetcher.fetch()); } catch (Exception e) { onFailure.onFailure(e); } }).start(); } } Executed on a different thread

Asynchronous call class AsyncFetcher { private final Fetcher fetcher; AsyncFetcher(Fetcher fetcher) { this.fetcher = fetcher; } void fetch(OnSuccess onSuccess, OnFailure onFailure) { new Thread(() -> { try { Thread.sleep(1000L); onSuccess.onSuccess(fetcher.fetch()); } catch (Exception e) { onFailure.onFailure(e); } }).start(); } } time intensive task

Asynchronous call class AsyncFetcher { private final Fetcher fetcher; AsyncFetcher(Fetcher fetcher) { this.fetcher = fetcher; } void fetch(OnSuccess onSuccess, OnFailure onFailure) { new Thread(() -> { try { Thread.sleep(1000L); onSuccess.onSuccess(fetcher.fetch()); } catch (Exception e) { onFailure.onFailure(e); } }).start(); } } Callbacks

Asynchronous Test public class AsyncFetcherTest { private Fetcher fetcher; private AsyncFetcher asyncFetcher; @Before public void setUp() throws Exception { fetcher = spy(new Fetcher.StringFetcher()); asyncFetcher = new AsyncFetcher<>(fetcher); } @Test public void fetch_success() throws Exception { asyncFetcher.fetch(); } }

Asynchronous Test public class AsyncFetcherTest { private Fetcher fetcher; private AsyncFetcher asyncFetcher; @Before public void setUp() throws Exception { fetcher = spy(new Fetcher.StringFetcher()); asyncFetcher = new AsyncFetcher<>(fetcher); } @Test public void fetch_success() throws Exception { asyncFetcher.fetch(); } }

Asynchronous Test public class AsyncFetcherTest { private Fetcher fetcher; private AsyncFetcher asyncFetcher; @Before public void setUp() throws Exception { fetcher = spy(new Fetcher.StringFetcher()); asyncFetcher = new AsyncFetcher<>(fetcher); } @Test public void fetch_success() throws Exception { asyncFetcher.fetch(); } } How do I write this test?

Asynchronous Test @Test public void fetch_success() throws Exception { asyncFetcher.fetch( result -> { assertThat(result).isEqualTo("OK"); log("async: ok"); }, e -> log("async: ng") ); log("fetch_success: end"); }

Asynchronous Test @Test public void fetch_success() throws Exception { asyncFetcher.fetch( result -> { assertThat(result).isEqualTo("OK"); log("async: ok"); }, e -> log("async: ng") ); log("fetch_success: end"); } success

Asynchronous Test @Test public void fetch_success() throws Exception { asyncFetcher.fetch( result -> { assertThat(result).isEqualTo("OK"); log("async: ok"); }, e -> log("async: ng") ); log("fetch_success: end"); } failure

Asynchronous Test @Test public void fetch_failure() throws Exception { doThrow(new RuntimeException("NG")).when(fetcher).fetch(); asyncFetcher.fetch( result -> log("async: ok"), e -> { assertThat(e.getMessage()).isEqualTo("NG"); log("async: ng"); } ); log("fetch_failure: end"); }

Asynchronous Test @Test public void fetch_failure() throws Exception { doThrow(new RuntimeException("NG")).when(fetcher).fetch(); asyncFetcher.fetch( result -> log("async: ok"), e -> { assertThat(e.getMessage()).isEqualTo("NG"); log("async: ng"); } ); log("fetch_failure: end"); } stub failure

Asynchronous Test Callback is NOT actually called!!! Execution seems successful...but wait?

Asynchronous Test private CountDownLatch latch; @Before public void setUp() throws Exception { fetcher = spy(new Fetcher.StringFetcher()); asyncFetcher = new AsyncFetcher<>(fetcher); latch = new CountDownLatch(1); }

Asynchronous Test Acts like an ON/OFF latch private CountDownLatch latch; @Before public void setUp() throws Exception { fetcher = spy(new Fetcher.StringFetcher()); asyncFetcher = new AsyncFetcher<>(fetcher); latch = new CountDownLatch(1); }

Asynchronous Test @Test public void fetch_success() throws Exception { asyncFetcher.fetch( result -> { assertThat(result).isEqualTo("OK"); log("async: ok"); latch.countDown(); }, e -> log("async: ng") ); latch.await(); log("fetch_success: end"); }

Asynchronous Test @Test public void fetch_success() throws Exception { asyncFetcher.fetch( result -> { assertThat(result).isEqualTo("OK"); log("async: ok"); latch.countDown(); }, e -> log("async: ng") ); latch.await(); log("fetch_success: end"); }

Asynchronous Test @Test public void fetch_success() throws Exception { asyncFetcher.fetch( result -> { assertThat(result).isEqualTo("OK"); log("async: ok"); latch.countDown(); }, e -> log("async: ng") ); latch.await(); log("fetch_success: end"); } Test execution awaits here

Asynchronous Test @Test public void fetch_success() throws Exception { asyncFetcher.fetch( result -> { assertThat(result).isEqualTo("OK"); log("async: ok"); latch.countDown(); }, e -> log("async: ng") ); latch.await(); log("fetch_success: end"); } Opens the latch and test goes again

Asynchronous Test @Test public void fetch_failure() throws Exception { doThrow(new RuntimeException("NG")).when(fetcher).fetch(); asyncFetcher.fetch( result -> log("async: ok"), e -> { assertThat(e.getMessage()).isEqualTo("NG"); log("async: ng"); latch.countDown(); } ); latch.await(); log("fetch_failure: end"); }

Asynchronous Test @Test public void fetch_failure() throws Exception { doThrow(new RuntimeException("NG")).when(fetcher).fetch(); asyncFetcher.fetch( result -> log("async: ok"), e -> { assertThat(e.getMessage()).isEqualTo("NG"); log("async: ng"); latch.countDown(); } ); latch.await(); log("fetch_failure: end"); } The same implementation as success

Asynchronous Test Callback is properly called!!! Log message seems correct!!

Additional info... • MockWebServer for OkHttp • TestSubscriber for RxJava • https://speakerdeck.com/srym/ hayaiyasuiumai-sutatoatupudemoshi-eru- retrofit-plus-rxjava-deshun-jian- apikutukinguresipi?slide=17 Check this slide & sample project

Best practices and tips

Best practices and tips • Use interface at the structural boundary • Use DI pattern for testability • Static is EVIL • Don't be a Mad Tester

Use interface at the structural boundary

Repository pattern public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository(LocalTweetDataSource localDataSource) { this.localDataSource = localDataSource; } public List getTimeline() { return localDataSource.getTimeline(); } }

Repository pattern public class LocalTweetDataSource { public List getTimeline() { List tweets = new ArrayList<>(); // some local DB interaction return tweets; } } Concrete data source

Repository pattern public interface LocalTweetDataSource { List getTimeline(); class SQLiteTweetDataSource implements LocalTweetDataSource { @Override public List getTimeline() { List tweets = new ArrayList<>(); // some local DB interaction return tweets; } } class MockTweetDataSource implements LocalTweetDataSource { @Override public List getTimeline() { return Arrays.asList(/* some mock data */); } } }

Repository pattern public interface LocalTweetDataSource { List getTimeline(); class SQLiteTweetDataSource implements LocalTweetDataSource { @Override public List getTimeline() { List tweets = new ArrayList<>(); // some local DB interaction return tweets; } } class MockTweetDataSource implements LocalTweetDataSource { @Override public List getTimeline() { return Arrays.asList(/* some mock data */); } } }

Repository pattern public interface LocalTweetDataSource { List getTimeline(); class SQLiteTweetDataSource implements LocalTweetDataSource { @Override public List getTimeline() { List tweets = new ArrayList<>(); // some local DB interaction return tweets; } } class MockTweetDataSource implements LocalTweetDataSource { @Override public List getTimeline() { return Arrays.asList(/* some mock data */); } } } Concrete data source with real DB interactions

Repository pattern public interface LocalTweetDataSource { List getTimeline(); class SQLiteTweetDataSource implements LocalTweetDataSource { @Override public List getTimeline() { List tweets = new ArrayList<>(); // some local DB interaction return tweets; } } class MockTweetDataSource implements LocalTweetDataSource { @Override public List getTimeline() { return Arrays.asList(/* some mock data */); } } } mock data source just for tests

Repository pattern public class TweetRepositoryTest { private TweetRepository tweetRepository; @Before public void setUp() throws Exception { LocalTweetDataSource localDataSource = mock(LocalTweetDataSource.class); when(localDataSource.getTimeline()).thenReturn( Arrays.asList( Tweet.bodyOf("foo"), Tweet.bodyOf("bar"), Tweet.bodyOf("baz"))); tweetRepository = new TweetRepository(localDataSource); } }

Repository pattern public class TweetRepositoryTest { private TweetRepository tweetRepository; @Before public void setUp() throws Exception { LocalTweetDataSource localDataSource = new LocalTweetDataSource.MockTweetDataSource(); tweetRepository = new TweetRepository(localDataSource); } } You can even get rid of Mockito dependency

Use DI pattern for testability

Use DI pattern public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository() { this.localDataSource = new LocalTweetDataSource.SQLiteTweetDataSource(); } public List getTimeline() { return localDataSource.getTimeline(); } }

Use DI pattern public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository() { this.localDataSource = new LocalTweetDataSource.SQLiteTweetDataSource(); } public List getTimeline() { return localDataSource.getTimeline(); } } mocking field is painful!!

Use DI pattern public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository() { this.localDataSource = new LocalTweetDataSource.SQLiteTweetDataSource(); } public List getTimeline() { return localDataSource.getTimeline(); } }

Use DI pattern public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository(LocalTweetDataSource localDataSource) { this.localDataSource = localDataSource; } public List getTimeline() { return localDataSource.getTimeline(); } }

Use DI pattern public class TweetRepository { private final LocalTweetDataSource localDataSource; public TweetRepository(LocalTweetDataSource localDataSource) { this.localDataSource = localDataSource; } public List getTimeline() { return localDataSource.getTimeline(); } } Putting dependency from outer

Use DI pattern • This is so-called DI pattern • DI pattern does NOT have to use DI library • DI library (e.g. Dagger2) is useful though e.g. Factory Pattern

Static is EVIL

Static is EVIL because... • Static has global scope • Mockito cannot mock static • Static is practically unnecessary This may cause order dependent bugs

Static is practically unnecessary @Singleton public class TweetRepository { private final LocalTweetDataSource localDataSource; @Inject public TweetRepository(LocalTweetDataSource localDataSource) { this.localDataSource = localDataSource; } public List getTimeline() { return localDataSource.getTimeline(); } }

Static is practically unnecessary @Singleton public class TweetRepository { private final LocalTweetDataSource localDataSource; @Inject public TweetRepository(LocalTweetDataSource localDataSource) { this.localDataSource = localDataSource; } public List getTimeline() { return localDataSource.getTimeline(); } } Use Dagger's annotations for handy singleton

Don't be a Mad Tester

Don't be a Mad Tester • Avoid to test EVERYTHING • Unit tests are NOT perfect • Gain maximum with minimum investment! Enjoy your test life!!!

Thank you for listening! • All illustrations by www.irasutoya.com • Special Thanks to @sumio_tym, @numa08 • Get the slides: https://goo.gl/ju66No • Get the materials: https://goo.gl/R5kBeN