Introduction of basic features of Mockito.

1. unit testing on the rocks!

2. Why mock?

3. Isolation

4. Example
AccountController
HellotxtManagement
+addAccount
+deleteAccount
...
...

5. Example
AccountController
HellotxtManagement
+addAccount
+deleteAccount
...
...

6. The no-so-good way
HellotxtManagement
...
HellotxtManagementMock
void addAccount(){
//do what I want
}
..

7. The no-so-good way
HellotxtManagement
...
HellotxtManagementMock HellotxtManagementMock2
void addAccount(){ void addAccount(){
//do what I want //now do this
} }
.. ..

8. The no-so-good way
HellotxtManagement
...
HellotxtManagementMock HellotxtManagementMock2 HellotxtManagementMock3
void addAccount(){ void addAccount(){ void addAccount(){
//do what I want //now do this //throw exception
} } }
.. .. ..

10. The mockito way

11. Test Workflow
1. Create Mock
2. Stub
3. Invoke
4. Verify
5. Assert expectations

12. Creating a Mock
import static org.mockito.Mockito.*;
...
// You can mock concrete classes, not only interfaces
LinkedList mockedList = mock(LinkedList.class);

13. Stubbing
// stubbing
when(mockedList.get(0)).thenReturn("first");
when(mockedList.get(1)).thenThrow(new RuntimeException());

14. What’s going on?
// following prints "first"
System.out.println(mockedList.get(0));
// following throws runtime exception
System.out.println(mockedList.get(1));
// following prints "null" because get(999) was not stubbed
System.out.println(mockedList.get(999));

15. Verify
// Although it is possible to verify a stubbed invocation, usually it's
// just redundant
// If your code cares what get(0) returns then something else breaks
// (often before even verify() gets executed).
// If your code doesn't care what get(0) returns then it should not be
// stubbed. Not convinced? See here.
verify(mockedList).get(0);

16. What about void
methods?
• Often void methods you just verify them.
//create my mock and inject it to my unit under test
DB mockedDb = mock(DB.class);
MyThing unitUnderTest = new MyThing(mockedDb);
//invoke what we want to test
unitUnderTest.doSothing();
//verify we didn't forget to save my stuff.
verify(mockedDb).save();

17. What about void
methods?
• Although you can also Stub them to throw
an exception.
@Test(expected = HorribleException.class)
public void test3() throws Exception {
// create my mock and inject it to my unit under test
Oracle oracleMock = mock(Oracle.class);
MyThing unitUnderTest = new MyThing(oracleMock);
String paradox = "This statement is false";
// stub
doThrow(new HorribleException()).when(oracleMock).thinkAbout(paradox);
unitUnderTest.askTheOracle(paradox);
}

18. Argument Matchers
when(hellotxtManagementMock.addAccount(Mockito.any(Session.class), Mockito.anyString(),
Mockito.anyMap(), Mockito.anyString())).thenReturn(account);

19. Custom Argument
Matcher
Mockito.when(hellotxtManagementMock.getAuthenticationInfo(Mockito.argThat(new IsValidSession()),
Mockito.eq(Networks.FACEBOOK))).thenReturn(expectedResult);
...
private class IsValidSession extends ArgumentMatcher<Session> {
@Override
public boolean matches(Object argument) {
return argument instanceof Session
&& ((Session) argument).getSessionId().equals(TestValues.VALID_SESSION_ID);
}
}

20. Argument Capture
ArgumentCaptor<Session> sessionCaptor = ArgumentCaptor.forClass(Session.class);
...
ModelAndView result = accountController.addAccount(json.toString(), sessionId, deviceType,
deviceId, networkId);
...
verify(hellotxtManagementMock).addAccount(sessionCaptor.capture(), Mockito.eq(networkId),
Mockito.eq(parameters), Mockito.eq(redirectUrl));
...
assertEquals(sessionId, sessionCaptor.getValue().getSessionId());
assertEquals(deviceType, sessionCaptor.getValue().getDevice().getType().name());
assertEquals(deviceId, sessionCaptor.getValue().getDevice().getUid());