How to use serializeMock method of org.mockitoutil.SimpleSerializationUtil class

You can call ArgumentCaptor.getAllValues() instead of getValue(). This will return all captured values:

Returns all captured values. Use it when capturing varargs or when the verified method was called multiple times.

In this case, it will return a List<String> containing 1 and 2.

The getValue() method only returns the last captured value:

Returns the captured value of the argument.

If the method was called multiple times then it returns the latest captured value

In your code, you can replace atLeastOnce() with the more precise times(2) since the mock was called 2 times. You don't need to have two distinct calls to verify to capture the arguments: Mockito will be able to capture all arguments passed to the mock with just one call.

TestMock mock = Mockito.mock(TestMock.class);
mock.doIt("1");
mock.doIt("2");

ArgumentCaptor<String> argument = ArgumentCaptor.forClass(String.class);
verify(mock, times(2)).doIt(argument.capture()); // verify that it was call 2 times and capture the values given

System.out.println(argument.getAllValues());

In Java 8 it is even simpler than all of the above:

when(mockObject.myMethod(anyString()))
    .thenAnswer(invocation -> 
        invocation.getArgumentAt(0, String.class));

I've never used Mockito, but want to learn, so here goes. If someone less clueless than me answers, try their answer first!

Mockito.when(reader.document(anyInt())).thenAnswer(new Answer() {
 public Object answer(InvocationOnMock invocation) {
     Object[] args = invocation.getArguments();
     Object mock = invocation.getMock();
     return document(fakeIndex((int)(Integer)args[0]));
     }
 });

You can use PowerMockito

See the example:

Second second = Mockito.mock(Second.class);
whenNew(Second.class).withNoArguments().thenReturn(second);

But re-factoring is better decision.

I stumbled upon this too and the answer is buried quite deep in the docs, so here it is.

Mockito optionally offers advanced mocking features like mocking final classes. For this to work, they use a different mechanism ("mock maker") that is considered experimental and therefore turned off by default. But:

As a convenience, the Mockito team provides an artifact where this mock maker is preconfigured. Instead of using the mockito-core artifact, include the mockito-inline artifact in your project.

First, I would split your test into 2 separate tests, because you are testing 2 quite different scenarios:

@Test
public void testSuccessfulLogin() throws Exception {
    RequestBuilder requestBuilder = formLogin().user("test@tester.de").password("test");
    mockMvc.perform(requestBuilder).andExpect(redirectedUrl("/home")).andExpect(status().isFound());
}

@Test
public void testHomepageThrows500() throws Exception {

    // configure a mock service in the controller to throw an exception

    RequestBuilder requestBuilder = formLogin().user("test@tester.de").password("test");
    mockMvc.perform(requestBuilder).andExpect(redirectedUrl("/home")).andExpect(status().is5xxServerError());
}

Your first test is that of the successful login scenario.

The second test, as you've worded it in your question, is that where the home page (assuming a controller) returns a HTTP 500.
To get to the home page, you still need to login - it's not the act of logging on that generates the error, its the controller itself once you've logged on.
To make the controller return a HTTP 500 you are going to need to simulate some error. Without seeing your controller, I can only guess there is some service that is injected in. In your test you should be able to provide a mock of that, and then configure the mock to throw an exception.

You should be able to inject a mock something like this:

@RunWith(SpringJUnit4ClassRunner.class)
@WebMvcTest(HomeController.class)
public class HomeControllerIntegrationTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private YourService yourService;

And then within your test do something like the following (I'm using the BDD methods of mockito):

@Test
public void testHomepageThrows500() throws Exception {

    given(yourService.someMethod()).willThrow(new Exception("something bad happened");

    RequestBuilder requestBuilder = formLogin().user("test@tester.de").password("test");
    mockMvc.perform(requestBuilder).andExpect(redirectedUrl("/home")).andExpect(status().is5xxServerError());
}

Reopening as requested, but the solution (use an ArgumentMatcher) is identical to the one in the linked answer. Naturally, you can't use an ArgumentCaptor when stubbing, but everything else is the same.

class OfficeWithId implements ArgumentMatcher<Office> {
  long id;

  OfficeWithId(long id) {
    this.id = id;
  }

  @Override public boolean matches(Office office) {
    return office.id == id;
  }

  @Override public String toString() {
    return "[Office with id " + id + "]";
  }
}

when(client.callApi(anyString(), argThat(new IsOfficeWithId(123L)))
    .thenReturn(responseOne);

Because ArgumentMatcher has a single method, you can even make it a lambda in Java 8:

when(client.callApi(anyString(), argThat(office -> office.id == 123L))
    .thenReturn(responseOne);

If you're already using Hamcrest, you can adapt a Hamcrest matcher using MockitoHamcrest.argThat, or use the built-in hasProperty:

when(client.callApi(
  anyString(),
  MockitoHamcrest.argThat(
    hasProperty("id", equalTo(123L)))))
  .thenReturn(responseOne);

You need to have prepared the class calling the constructor, not the class on which the constructor is called, the following should fix you up:

@PrepareForTest(DummyTarget.class)

For more information check this page.

You need to move @EnableJpaAuditing annotation to a separate @Configuration class otherwise it will be loaded even for unrelated application slices.

@Configuration
@EnableJpaAuditing
public class JpaAuditingConfiguration {}

@SpringBootApplication class is used as default configuration for all tests with slices so any additional configuration glued to it will affect more tests than you would expect.

This is also well explained in documentation: User Configuration and Slicing