Mock objects

mock-objects

Unit testing with Mock objects using Mockito
--------------------------------------------
2 concepts
- mock (create object using mocks)
- stub (modify a created object with stub). useful methods when stubbing are:
    - when
    - doReturn
    
How mock object works
---------------------
- First, we define a Mock object that implements the same interface as an object on which the SUT (domain object) depends
- Then during the test, we configure the Mock object with the values with which it should respond to the SUT
- Before exercising the SUT, we install the Mock object so that the SUT uses it instead of the real implementation
- When called during SUT execution, the Mock object compares the actual arguments received wth the expected arguments using Equality Assertions

Implementation steps (notes) for mock object
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- Test constructs Mock Object
- Test configures Mock Object
- Test installs Mock Object into domain object (SUT) - Make Mock Object a dependency e.g by annotating it or instantiating the mock object
- SUT calls Mock Object (happens in the background)
- Mock object does assertions
- Test calls final verification method

Mock example without a framework
--------------------------------
public void testRemoveFlight_Mock() throws Exception {
    // fixture setup
    FlightDto expectedFlightDto = createAnonRegFlight();
    // mock configuration
    ConfigurableMockAuditLog mockLog = new ConfigurableMockAuditLog();
    mockLog.setExpectedLogMessage(
        helper.getTodaysDateWithoutTime(),
        Helper.TEST_USER_NAME,
        Helper.REMOVE_FLIGHT_ACTION_CODE,
        expectedFlightDto.getFlightNumber());
    mockLog.setExpectedNumberCalls(1);
    
    // mock installation
    FlightManagementFacade facade = new FlightManagementFacadeImpl();
    facade.setAuditLog(mockLog);
    // exercise
    facade.removeFlight(expectedFlightDto.getFlightNumber());
    // verify
    assertFalse("flight still exists after being removed",
        facade.flightExists(expectedFlightDto.getFlightNumber()));
    mockLog.verify();
}
 
Mock example using a framework
------------------------------
public void testRemoveFlight_JMock() throws Exception {
    // fixture setup
    FlightDto expectedFlightDto = createAnonRegFlight();
    FlightManagementFacade = new FlightManagementFacadeImpl();
    // mock configuration
    Mock mockLog = mock(AuditLog.class);
    moclLog.expects(once()).method("logMessage)
        .with(eq(helper.getTodaysDateWithoutTime()),
            eq(Helper.TEST_USER_NAME),
            eq(Helper.REMOVE_FLIGHT_ACTION_CODE),
            eq(expectedFlightDto.getFlightNumber()));
            
    // mock installation
    facade.setAuditLog(AuditLog) mocklog.proxy())
    // exercise
    facade.removeFlight(expectedFlightDto.getFlightNumber());
    // verify
    assertFalse("flight still exists after being removed",
        facade.flightExists(expectedFlightDto.getFlightNumber()));
        
    // verify() method called automatically by JMock
}

Understanding the execution process of a Mock object
----------------------------------------------------
- When the SUT calls the methods of the Mock Object, the methods compare the method call (method name plus arguments) with the expectations. If the method call is unexpeced or the arguments are incorrect, the assertion fails the test immediately
- If the call is expected but came out of sequence (a reason to use Inorder), a strict Mock Object fails the test
- If the method call has any outgoing parameters or return values, the Mock Object needs to return or update something to allow the SUT to continue executing the test scenario.

Unit test and mock objects in Jive
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- JiveCommunityTest or one of it's subclasses must be extended by your test class in order to be able to run a test in Jive successfully
- When running test with JiveCommunityTest, it cannot be run with (RunWith) powermock since it's already running with @Refreshable (com.jivesoftware.util.junit.runners.Refreshable)