How to use testMockDispatcherIsRelocated method of org.mockito.internal.creation.bytebuddy.InlineDelegateByteBuddyMockMakerTest class

You can set a default answer for a mock. All methods that aren't stubbed will use this default answer.

public void testUnstubbedException() {
    // Create a mock with all methods throwing a RuntimeException by default
    SomeClass someClass = mock( SomeClass .class, new RuntimeExceptionAnswer() );

    doReturn(1).when(someClass).getId(); // Must use doReturn

    int id = someClass.getId(); // Will return 1

    someClass.unstubbedMethod(); // Will throw RuntimeException
}

public static class RuntimeExceptionAnswer implements Answer<Object> {

    public Object answer( InvocationOnMock invocation ) throws Throwable {
        throw new RuntimeException ( invocation.getMethod().getName() + " is not stubbed" );
    }

}

Note that you cannot use when with this functionality, since the method is called before when (How does mockito when() invocation work?) and it will throw a RuntimeException before the mock goes into stubbing mode.

Therefore, you must use doReturn for this to work.

Ok, I think I found the answer, but it was a headache. Rudy gave me the final hint with using using a spy, but it was still not trivial (although the solution looks "baby-easy"). Here is the complete solution:

import static org.mockito.Matchers.anyString;
import static org.mockito.Mockito.times;
import static org.powermock.api.mockito.PowerMockito.verifyPrivate;
import static org.powermock.api.mockito.PowerMockito.doNothing;
import static org.powermock.api.mockito.PowerMockito.spy;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Factory.class)
public class Tests extends TestCase {

    public void testFactory() throws Exception {

        Factory factorySpy = spy(new Factory());
        String s = factorySpy.factorObject();
        doNothing().when(factorySpy, "checkString", anyString());
        verifyPrivate(factorySpy, times(1)).invoke("checkString", anyString()); 
    }
}

Instead of creating a equals method in your BPRequestVO class you can create a mock argument with "any(YourObject.class)" like this:

when(mockBPService.getProduct(any(BPRequestVO.class))).thenReturn(invalidServiceResponse);

Wire Mock seems to offer a solid set of stubs and mocks for testing external web services.

@Rule
public WireMockRule wireMockRule = new WireMockRule(8089);


@Test
public void exactUrlOnly() {
    stubFor(get(urlEqualTo("/some/thing"))
            .willReturn(aResponse()
                .withHeader("Content-Type", "text/plain")
                .withBody("Hello world!")));

    assertThat(testClient.get("/some/thing").statusCode(), is(200));
    assertThat(testClient.get("/some/thing/else").statusCode(), is(404));
}

It can integrate with spock as well. Example found here.

This is the expected behavior, when you mock something the created instance is a complete mock, so it makes no sense to initialize the fields as behavior is defaulted.

Aside of that, fields can be initialized by a constructor in concrete or abstract classes, as mocks instantiation bypasses the constructor simply because it's a mock, it is even more irrational to initialize them.

Trying to call the real method is usually wrong when using mocks. Instead one should stub the behavior of the mock.

Mockito.when(foo.isNull(Mockito.anyObject())).thenReturn(false);
Assert.assertFalse(foo.isNull("baaba")); // assertion always passing

I don't know your actual use case but maybe you want a partial mock, with a spy. Though that's still considered bad practice as it usually means you need to refactor the code to use composition.

As a starting point and demonstration for the principal you can start with the following snippet.

// define the headers you want to be returned
Map<String, String> headers = new HashMap<>();
headers.put(null, "HTTP/1.1 200 OK");
headers.put("Content-Type", "text/html");

// create an Enumeration over the header keys
Enumeration<String> headerNames = Collections.enumeration(headers.keySet());

// mock HttpServletRequest
HttpServletRequest request = mock(HttpServletRequest.class);
// mock the returned value of request.getHeaderNames()
when(request.getHeaderNames()).thenReturn(headerNames);

System.out.println("demonstrate output of request.getHeaderNames()");
while (headerNames.hasMoreElements()) {
    System.out.println("header name: " + headerNames.nextElement());
}
    
// mock the returned value of request.getHeader(String name)
doAnswer(new Answer<String>() {
    @Override
    public String answer(InvocationOnMock invocation) throws Throwable {
        Object[] args = invocation.getArguments();
        return headers.get((String) args[0]);
    }
}).when(request).getHeader("Content-Type");

System.out.println("demonstrate output of request.getHeader(String name)");
String headerName = "Content-Type";
System.out.printf("header name: [%s]   value: [%s]%n", 
        headerName, request.getHeader(headerName));
}

Output

demonstrate output of request.getHeaderNames()
header name: null
header name: Content-Type

demonstrate output of request.getHeader(String name)
header name: [Content-Type]   value: [text/html]

OK. So, the contract of the method is the following: Parse the input string as JSON, and send back BAD_REQUEST if it's invalid. If it's valid, create an entity in the datastore with various properties (you know them), and send back OK.

And you need to verify that this contract is fulfilled by the method.

Where does Mockito help here? Well, if you test this method without Mockito, you need a real DataStoreService, and you need to verify that the entity has been created correctly in this real DataStoreService. This is where your test is not a unit test anymore, and this is also where it's too complex to test, too long, and too hard to run because it needs a complex environment.

Mockito can help by mocking the dependency on the DataStoreService: you can create a mock of DataStoreService, and verify that this mock is indeed called with the appropriate entity argument when you call your initialize() method in your test.

To do that, you need to be able to inject the DataStoreService into your object under test. It can be as easy as refactoring your object in the following way:

public class MyRestService {
    private DataStoreService dataStoreService;

    // constructor used on the server
    public MyRestService() {
        this.dataStoreService = DatastoreServiceFactory.getDatastoreService();
    }

    // constructor used by the unit tests
    public MyRestService(DataStoreService dataStoreService) {
        this.dataStoreService = dataStoreService;
    }

    public Response initialize(String DatabaseSchema) {
         ...
         // use this.dataStoreService instead of datastore
    }
}

And now in your test method, you can do:

@Test
public void testInitializeWithGoodInput() {
    DataStoreService mockDataStoreService = mock(DataStoreService.class);
    MyRestService service = new MyRestService(mockDataStoreService);
    String goodInput = "...";
    Response response = service.initialize(goodInput);
    assertEquals(Response.Status.OK, response.getStatus());

    ArgumentCaptor<Entity> argument = ArgumentCaptor.forClass(Entity.class);
    verify(mock).put(argument.capture());
    assertEquals("the correct kind", argument.getValue().getKind());
    // ... other assertions
}

This is possible using Mockito.when:

Mockito.when(statusRepository.delete(any(Post.class)).thenReturn(Mono.empty());

...call the method and verify...

Mockito.verify(statusRepository).delete(any(Post.class));

The parentheses are poorly placed.

You need to use:

doThrow(new Exception()).when(mockedObject).methodReturningVoid(...);
                                          ^

and NOT use:

doThrow(new Exception()).when(mockedObject.methodReturningVoid(...));
                                                                   ^

This is explained in the documentation