Unit Testing in a Nutshell - DroidKaigi 2018

Unit Testing in a Nutshell - DroidKaigi 2018
This is a reference material for this session
https://droidkaigi.jp/2018/timetable?session=16942
Hands-On
https://github.com/srym/DroidKaigi2018UnitTestHandOn

Transcript

1. Unit Testing in a Nutshell
   Fumihiko Shiroyama
   DroidKaigi 2018
   

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

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3. 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
   

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4. Why you should care about Unit Testing?
   

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5. What if you DON'T?
   

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6. public class LoginActivity extends AppCompatActivity implements LoaderCallbacks {
   private static final int REQUEST_READ_CONTACTS = 0;
   private static final String[] DUMMY_CREDENTIALS = new String[]{
   "foo@example.com:hello", "bar@example.com: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);
   }
   }
   

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7. public class LoginActivity extends AppCompatActivity implements LoaderCallbacks {
   private static final int REQUEST_READ_CONTACTS = 0;
   private static final String[] DUMMY_CREDENTIALS = new String[]{
   "foo@example.com:hello", "bar@example.com: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!!
   

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

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

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10. Is unit testing just enough?
    

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11. No!!
    It just ensures it partially worked
    

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

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13. anyway
    

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14. JUnit4 and basic assertions
    

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15. 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
    

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16. Assertions
    

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17. 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");
    

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18. 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
    

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19. 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
    

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20. Create New Test
    Command + SHIFT + T
    

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21. Create New Test
    

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22. Create New Test
    

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

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

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

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

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

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28. This session only cares
    Local Unit Tests
    

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

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

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

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32. 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
    

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

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34. 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
    

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35. 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
    

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36. 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
    

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37. 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
    

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38. 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
    

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39. 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"
    

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40. 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
    

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41. 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
    

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42. 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();
    }
    }
    

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43. Run tests
    Run single
    Run all
    or
    Passed!!!!
    

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

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45. Congrats!!!
    

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

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47. • 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
    

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

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49. Exceptions
    

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50. 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;
    }
    }
    

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51. 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
    

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

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

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

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

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56. 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
    

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57. 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
    

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58. 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;
    }
    }
    

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59. 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!!
    

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

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61. Mock and spy with Mockito
    

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

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

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64. Test Doubles
    They are
    

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65. Why you need mocks?
    

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

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67. 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
    

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

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69. 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!
    

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70. 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
    

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71. Mockito
    

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

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73. 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
    

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74. Stubbing
    

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75. 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")
    )
    );
    

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76. 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")
    )
    );
    

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77. 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")
    )
    );
    

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78. 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
    

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

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

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

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

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

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84. 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
    

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85. 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
    

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86. 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")
    )
    );
    

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87. 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);
    }
    

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88. 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);
    }
    

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89. 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")
    );
    }
    

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90. 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")
    );
    }
    

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91. 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")
    );
    }
    

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92. 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")
    );
    }
    

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93. 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!!
    

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94. Spying
    

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

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96. 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());
    

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97. 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
    

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98. 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()
    

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99. 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
    

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

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101. 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());
     

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102. 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());
     

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103. 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());
     

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104. 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());
     

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105. 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());
     

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106. 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());
     

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107. 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!
     

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108. 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());
     

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109. 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());
     

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110. 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
     

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111. 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
     

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

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113. 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
     

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

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115. 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");
     

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116. 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");
     

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117. 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");
     

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118. 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
     

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119. 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
     

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120. Stubbing spy method
     

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121. 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
     

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122. 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
     

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123. 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");
     

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124. 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");
     

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125. 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");
     

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126. 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");
     

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127. 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!
     

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128. Stubbing void method
     

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

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

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

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

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

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

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

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

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

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

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139. Robolectric for framework's code
     

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140. 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;
     }
     }
     

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141. 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;
     }
     }
     

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142. 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
     

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143. 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();
     }
     }
     

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

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

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146. 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
     

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147. 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
     

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148. Robolectric
     

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149. 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
     

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

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151. 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);
     }
     }
     

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152. 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!!
     

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153. 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
     }
     }
     

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154. 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!!
     

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155. • 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
     

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156. Unit Testing SQLite
     

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

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

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159. 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
     

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160. 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
     

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

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162. 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
     

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163. 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
     

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164. 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
     

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165. 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
     

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166. 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);
     }
     }
     

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167. 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);
     }
     }
     

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168. 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);
     }
     }
     

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169. 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);
     }
     }
     

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170. 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);
     }
     }
     

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171. 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);
     }
     }
     

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172. 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
     

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173. 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
     

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174. Unit Testing asynchronous code
     

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

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

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

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178. 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
     

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179. 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();
     }
     }
     

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180. 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();
     }
     }
     

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181. 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
     

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182. 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
     

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183. 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
     

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184. 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();
     }
     }
     

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185. 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();
     }
     }
     

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186. 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?
     

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187. 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");
     }
     

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188. 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
     

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189. 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
     

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190. 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");
     }
     

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191. 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
     

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

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

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194. 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);
     }
     

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195. 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");
     }
     

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196. 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");
     }
     

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197. 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
     

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198. 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
     

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199. 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");
     }
     

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200. 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
     

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

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202. 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
     

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203. Best practices and tips
     

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

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205. Use interface
     at the structural boundary
     

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

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

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208. 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 */);
     }
     }
     }
     

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209. 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 */);
     }
     }
     }
     

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210. 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
     

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211. 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
     

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212. 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);
     }
     }
     

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213. 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
     

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214. Use DI pattern for testability
     

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

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216. 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!!
     

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

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

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219. 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
     

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220. 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
     

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221. Static is EVIL
     

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

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223. 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();
     }
     }
     

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224. 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
     

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225. Don't be a Mad Tester
     

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

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227. 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
     

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