Testing made sweet with a Mockito

Transcript

TESTING MADE SWEET
WITH A MOCKITO
@MOLSJEROEN

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@MOLSJEROEN
@MOLSJEROEN

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IF YOU DON’T LIKE UNIT TESTING YOUR
PRODUCT, MOST LIKELY YOUR CUSTOMERS
WON’T LIKE TO TEST IT EITHER.
Unknown

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ALWAYS WRITE A TEST TO REPRODUCE A
BUG BEFORE YOU FIX IT
Robert C. Martin*

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@MOLSJEROEN
GOAL
UI
USER
WEBSERVICE
Button press
Login/logout command Success/failure
Update UI LOGININTERFACE
RESPONSE

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@MOLSJEROEN
GOAL
UI
USER
WEBSERVICE
Button press
Login/logout command Success/failure
Update UI LOGININTERFACE
RESPONSE

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WAY OF WORKING

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@MOLSJEROEN
TEST REQUIREMENTS
▸ All tests must
▸ Run really fast
▸ Be small and focussed
▸ Reliable, not “ﬂaky”
▸ Challenges: UI & WebService
UI
USER
WEBSERVICE

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@MOLSJEROEN
SOLUTION
▸ Isolate User
▸ Don’t include UI
▸ Replace WebService with dummy
▸ Mimic WebService behaviour
▸ => Verify interactions
UI
USER
WEBSERVICE*

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@MOLSJEROEN
DEFINITION: TEST DOUBLES
▸ Replace real class
▸ Same interface
▸ Different behaviour
WEBSERVICE*
WEBSERVICE
public void login() {
 
// NORMAL IMPL.
 
}
 
// DO NOTHING
 
}

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@MOLSJEROEN
▸ Same interface
WEBSERVICE*
WEBSERVICE
 
// NORMAL IMPL.
 
}
 
// DO NOTHING
 
}

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@MOLSJEROEN
▸ Same interface
WEBSERVICE*
WEBSERVICE
 
// NORMAL IMPL.
 
}
 
loginInterface.success();
 
}

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@MOLSJEROEN
▸ Same interface
WEBSERVICE*
WEBSERVICE
 
// NORMAL IMPL.
 
}
 
throw new Exception();
 
}

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@MOLSJEROEN
DEFINITION: MOCKS AND STUBS
▸ What is a mock?
▸ Generated class
▸ Doesn’t do anything
▸ Behaviour verification
▸ What is a stub?
▸ Handwritten class
▸ Returns predefined responses
▸ State verification

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MOCKITO

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@MOLSJEROEN
Open source mocking framework that lets you write
beautiful tests with a clean & simple API
▸ Documentation on mockito.org
▸ Source code on Github
▸ MIT license
WHAT IS IT?

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@MOLSJEROEN
WHY DRINK IT?
▸ Easy to use
▸ Very readable syntax
▸ No learning curve
▸ Annotation support
▸ Mature
▸ Large stackoverﬂow community
▸ Most popular Java / Android mocking framework

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@MOLSJEROEN
HOW TO DRINK IT?
▸ PROJECT_HOME/build.gradle
buildscript { 
repositories { 
jcenter() 
} 
} 
 
▸ MODULE_HOME/build.gradle
dependencies { 
...
 
testCompile "org.mockito:mockito-core:2.0.101-beta" 
}

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@MOLSJEROEN
HOW TO DRINK IT?
▸ PROJECT_HOME/build.gradle
buildscript { 
repositories { 
jcenter() 
} 
} 
 
dependencies { 
...
 
testCompile "org.mockito:mockito-core:2.0.101-beta" 
}

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INGREDIENTS

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@MOLSJEROEN
INGREDIENTS
▸ Creating a mock
▸ Verifying interactions
▸ Stubbing methods
▸ Capturing arguments
▸ Mockito limitations

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@MOLSJEROEN
INGREDIENTS
▸ Creating a mock

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@MOLSJEROEN
CREATING A MOCK
import static org.mockito.Mockito.mock;
@Test 
public void createMock() throws Exception { 
WebService mockWebService = mock(WebService.class); 
 
new User(mockWebService, 0, null); 
}

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@MOLSJEROEN
CREATING A MOCK
@Test 
 
}

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@MOLSJEROEN
CREATING A MOCK
@Test 
 
}

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@MOLSJEROEN
CREATING A MOCK - ANNOTATION
@Rule 
public MockitoRule mockitoRule = MockitoJUnit.rule(); 
 
@Mock 
private WebService mockWebService;
@Test 
public void createMockUsingAnnotation() throws Exception { 
}

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@MOLSJEROEN
@Rule 
 
@Mock 
@Test 
}

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@MOLSJEROEN
@Rule 
 
@Mock 
@Test 
}

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@MOLSJEROEN
INGREDIENTS
▸ Creating a mock

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@MOLSJEROEN
VERIFYING INTERACTIONS
@Test 
public void verifyInteractionTimes() throws Exception { 
User user = new User(mockWebService, USER_ID, PASSWORD); 
 
user.logout(); 
 
verify(mockWebService).logout(); 
}

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@MOLSJEROEN
VERIFYING INTERACTIONS
@Test 
 
user.logout(); 
 
verify(mockWebService).logout(); 
}

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@MOLSJEROEN
VERIFYING INTERACTIONS - TIMES
@Test 
 
user.logout(); 
 
verify(mockWebService, times(1) ).logout(); 
atLeast(1) 
atLeastOnce() 
atMost(1) 
only() 
never() 
}

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@MOLSJEROEN
VERIFYING INTERACTIONS - TIMES
@Test 
 
user.logout(); 
 
verify(mockWebService, times(1) ).logout(); 
atLeast(1) 
atLeastOnce() 
atMost(1) 
only() 
never() 
}
▸ Being overly restrictive makes tests brittle!

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@MOLSJEROEN
VERIFYING INTERACTIONS - PARAMETERS
@Test 
public void verifyInteractionParameters() throws Exception { 
 
user.login(null); 
 
verify(mockWebService).login(USER_ID); 
}

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@MOLSJEROEN
@Test 
 
 
verify(mockWebService).login(anyInt() );
anyString()
any(Response.class) 
}

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@MOLSJEROEN
@Test 
 
 
verify(mockWebService).login(anyInt(), eq(PASSWORD)); 
}
▸ One matcher -> all arguments need to be matchers

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@MOLSJEROEN
@Test 
 
 
verify(mockWebService).login(gt(0) ); 
lt(10000)
leq(10000) 
}

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@MOLSJEROEN
@Test 
 
 
verify(mockWebService).login(startsWith(“n1") ); 
contains(“c3")
matches("n[1-9]{1}c[1-9]{1}[a-z]{3}")
}

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@MOLSJEROEN
@Test 
 
 
verify(mockWebService).login(isNotNull(Response.class)) );
not(eq(0))
not(eq(“12345678"))
and(gt(0), lt(Integer.MAX_VALUE)) 
}
▸ Mockito.Matchers
▸ Mockito.AdditionalMatchers

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@MOLSJEROEN
VERIFYING INTERACTIONS - ORDER
@Test 
public void verifyInteractionOrder() throws Exception { 
 
user.logout(); 
 
InOrder inOrder = inOrder(mockWebService); 
inOrder.verify(mockWebService).login(); 
inOrder.verify(mockWebService).logout(); 
}

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@MOLSJEROEN
@Test 
 
user.logout(); 
 
}

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@Test 
 
user.logout(); 
 
}

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@MOLSJEROEN
INGREDIENTS
▸ Creating a mock

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@MOLSJEROEN
STUBBING METHODS
@Test 
public void stubMethod() throws Exception { 
when(mockWebService.isOffline()).thenReturn(true); 
 
user.login(mockLoginInterface); 
 
verify(mockWebService, never()).login(); 
}

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@MOLSJEROEN
STUBBING METHODS
@Test 
 
 
}

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@MOLSJEROEN
STUBBING METHODS
@Test 
 
 
}

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@MOLSJEROEN
STUBBING METHODS
@Test 
when(mockWebService.isOffline()).thenReturn(true, false, true); 
 
 
}

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@MOLSJEROEN
STUBBING METHODS
@Test 
when(mockWebService.isOffline()).thenThrow(CustomException.class); 
 
 
}

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@MOLSJEROEN
STUBBING METHODS
▸ Normal syntax
when(mockWebService.isOffline()).thenReturn(true);
 
▸ Alternative syntax
doReturn(true).when(mockWebService).isOffline();
 
▸ BDD syntax
given(mockWebService.isOffline()).willReturn(true);

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@MOLSJEROEN
STUBBING METHODS
▸ Normal syntax
 
 
▸ BDD syntax

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@MOLSJEROEN
STUBBING METHODS
▸ Normal syntax
 
 
▸ BDD syntax

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@MOLSJEROEN
INGREDIENTS
▸ Creating a mock

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@MOLSJEROEN
CAPTURING ARGUMENTS
@Test 
public void captureArguments() throws Exception { 
verify(mockWebService).login(responseArgumentCaptor.capture()); 
Response response = responseArgumentCaptor.getValue(); 
 
response.onRequestCompleted(true); 
 
verify(mockLoginInterface).onLoginSuccess(); 
}
UI USER WEBSERVICE
LOGININTERFACE RESPONSE

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@MOLSJEROEN
CAPTURING ARGUMENTS
@Captor 
private ArgumentCaptor responseArgumentCaptor;
UI USER WEBSERVICE

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@MOLSJEROEN
CAPTURING ARGUMENTS
@Test 
 
 
}
UI USER WEBSERVICE

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@MOLSJEROEN
CAPTURING ARGUMENTS
@Test 
 
 
}
UI USER WEBSERVICE

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@MOLSJEROEN
CAPTURING ARGUMENTS
@Test 
 
 
}
UI USER WEBSERVICE

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@MOLSJEROEN
CAPTURING ARGUMENTS
@Test 
 
 
}
UI USER WEBSERVICE

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@MOLSJEROEN
INGREDIENTS
▸ Creating a mock

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@MOLSJEROEN
MOCKITO LIMITATIONS
▸ Unable to mock
▸ ﬁnal classes
▸ ﬁnal methods
▸ static methods
▸ private methods
▸ hashCode() and equals()

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ADVANCED MOCKITO

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@MOLSJEROEN
▸ Model View Presenter
▸ Mock view & model
▸ Fully test presenter
▸ UI layer == “pass through”
▸ Dependency injection
▸ Only “inward pointing” dependencies
1. TESTING UI
MODEL
VIEW
VIEW
IMPLEMENTATION PRESENTER

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@MOLSJEROEN
2. RUNNING MOCKITO ON A DEVICE
defaultConfig { 
…
 
testInstrumentationRunner  
"android.support.test.runner.AndroidJUnitRunner" 
}
dependencies { 
…
 
androidTestCompile 'com.android.support.test:runner:0.4' 
androidTestCompile 'com.android.support.test:rules:0.4' 
androidTestCompile 'org.mockito:mockito-core:1.10.19' 
androidTestCompile "com.google.dexmaker:dexmaker:1.2" 
androidTestCompile "com.google.dexmaker:dexmaker-mockito:1.2" 
}

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@MOLSJEROEN
defaultConfig { 
…
 
}
dependencies { 
…
 
}

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@MOLSJEROEN
defaultConfig { 
…
 
}
dependencies { 
…
 
}

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@MOLSJEROEN
3. TESTING FINAL METHODS / CLASSES
public class Handler { 
 
public Handler() {}; 
 
public final boolean post(Runnable r) 
{ 
// internal implementation 
} 
 
public final boolean sendMessage(Message msg) 
{ 
} 
}

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@MOLSJEROEN
public class Handler { 
 
public Handler() {}; 
 
public final boolean post(Runnable r) 
{ 
} 
 
public final boolean sendMessage(Message msg) 
{ 
} 
}

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@MOLSJEROEN
public class HandlerWrapper { 
 
private final Handler handler; 
 
public HandlerWrapper() { 
handler = new Handler(); 
} 
 
public boolean post(Runnable r) { 
return handler.post(r); 
} 
 
public boolean sendMessage(Message msg) { 
return handler.sendMessage(msg); 
} 
}

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@MOLSJEROEN
 
 
} 
 
} 
 
} 
}

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@MOLSJEROEN
 
 
} 
 
} 
 
} 
}

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@MOLSJEROEN
3. TESTING STATIC METHODS
public class NativeCamera { 
 
private Camera camera = null; 
 
public Camera getNativeCamera() { 
return camera; 
} 
 
public void openNativeCamera() throws RuntimeException { 
camera = Camera.open(CameraInfo.CAMERA_FACING_BACK); 
} 
 
public void releaseNativeCamera() { 
camera.release(); 
} 
}

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@MOLSJEROEN
3. TESTING STATIC METHODS
public class NativeCamera { 
 
private Camera camera = null; 
 
public Camera getNativeCamera() { 
return camera; 
} 
 
public void openNativeCamera() throws RuntimeException { 
camera = Camera.open(CameraInfo.CAMERA_FACING_BACK); 
} 
 
public void releaseNativeCamera() { 
camera.release(); 
} 
}

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@MOLSJEROEN
4. TESTING DATA
@Test 
public void mockData() throws Exception { 
UserData mock = mock(UserData.class); 
when(mock.getFirstName()).thenReturn("FirstName"); 
when(mock.getLastName()).thenReturn("LastName"); 
when(mock.getUserId()).thenReturn(1111007); 
 
when(mock.getStreet()).thenReturn("StreetName"); 
when(mock.getHouseNumber()).thenReturn(1); 
when(mock.getCity()).thenReturn("City"); 
when(mock.getCountry()).thenReturn("Country"); 
 
// Use mock in further test 
}

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@MOLSJEROEN
4. TESTING DATA
@Test 
public void testData() throws Exception { 
UserData userData = new TestUserData(); 
 
// use mock in further test 
}
public class TestUserData extends UserData {
@Override 
public String getFirstName() { 
return "FirstName"; 
}
 
...
}

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@MOLSJEROEN
4. TESTING DATA
@Test 
public void testData() throws Exception { 
UserData userData = new TestUserData(); 
 
// use mock in further test 
}
public class TestUserData extends UserData {
@Override 
public String getFirstName() { 
return "FirstName"; 
}
 
...
}

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@MOLSJEROEN
5. NEW CREATION
public User(int userId, String password) { 
this.webService = new WebService(); 
}
▸ Internal created objects
▸ almost impossible to test
▸ avoid for long lived objects

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@MOLSJEROEN
5. NEW CREATION
}
▸ Internal created objects
▸ almost impossible to test
▸ avoid for long lived objects

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@MOLSJEROEN
5. NEW CREATION
}
▸ Dependency injection
public User(WebService webService, int userId, String password) { 
if (webService == null) { 
throw new RuntimeException("Webservice required"); 
} 
this.webService = webService; 
}

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@MOLSJEROEN
5. NEW CREATION
}
▸ Factory pattern
public User(WebServiceFactory factory, int userId, String password) { 
this.webService = factory.createWebService(); 
}

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@MOLSJEROEN
6. POWER TIPS
▸ Avoid singletons
▸ Avoid instrumentation tests
▸ Isolate non testable code
▸ Don’t use Spies
▸ Don’t nest mocks
▸ Avoid using “For testing methods”

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WRAP UP

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IT IS BETTER TO HAVE A SIMPLE TEST
THAT WORKS THAN A COMPLICATED
TEST THAT SEEMS TO WORK.
Mockito documentation

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@MOLSJEROEN
CONCLUSION
▸ Mockito makes mocking & stubbing easy
▸ Avoid creating internal objects
▸ Choose a good testing strategy
▸ Don’t overuse the power features
▸ Keep unit tests small and focussed
▸ Consider refactoring
▸ Prefer tests on the java VM

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@MOLSJEROEN
REFERENCES
▸ Mockito homepage http://mockito.org/
▸ Mockito reference card https://dzone.com/refcardz/mockito
▸ Dexmaker https://github.com/crittercism/dexmaker
▸ Sample code
▸ MockitoExample https://github.com/JeroenMols/MockitoExample
▸ LandscapeVideoCamera https://github.com/JeroenMols/LandscapeVideoCamera
▸ Legofy https://github.com/JeroenMols/Legofy

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@MOLSJEROEN
IMAGE CREDITS
▸ Mojito 
https://indraneescookingcorner.blogspot.be/2014/08/virgin-mojito.html
▸ Philips Hue living room 
http://www.philips.de
▸ Bartender set 
http://www.vinspireuk.com/2014/12/cocktail-gifts-for-cocktail-lovers.html
▸ Mojito ingredients 
https://www.nelleulla.com/lv-en/products/trufﬂes/4-mojito-trufﬂe
▸ Mockito Mojito 
http://www.seedylawyer.com/history-of-hemingways-mojitos/
▸ Raspberry Mojito 
http://goodpixcool.com/raspberry+mojito+in+a+bottle?image=99002602
▸ Drinking Mojito 
https://www.lancerskincare.com/blog/10-ways-to-age-your-skin-prematurely/

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@MOLSJEROEN
MANY THANKS
▸ Jeroen Mols (Belgium)
▸ @MolsJeroen
▸ http://jeroenmols.com/blog

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Testing made sweet with a Mockito

Testing made sweet with a Mockito

Jeroen Mols

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