List of Classes and Methods of org.mockitousage.debugging package of Mockito Framework

Consider overriding your Guice injection configuration using another test module.

I will show it using own example, but it's easy to adapt to your needs.

Module testModule = Modules.override(new ProductionModule())
    .with(new AbstractModule(){

    @Override
    protected void configure() {
        bind(QueueFactory.class).toInstance(spy(new QueueFactory()));
    }

});

Injector injector = Guice.createInjector(testModule);
QueueFactory qFactorySpy = injector.getInstance(QueueFactory.class);

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]

For those who are using the newer version of swagger, here is the solution for accessing the swagger ui page.

Replace this:

    <dependency>
        <groupId>io.springfox</groupId>
        <artifactId>springfox-swagger2</artifactId>
        <version>2.8.0</version>
  </dependency>
    <!-- https://mvnrepository.com/artifact/io.springfox/springfox-swagger-ui -->
    <dependency>
        <groupId>io.springfox</groupId>
        <artifactId>springfox-swagger-ui</artifactId>
        <version>2.8.0</version>
    </dependency>

with this:

<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-boot-starter</artifactId>
    <version>3.0.0</version>
</dependency>

in your pom.xml file.

Access the page via the following url (avoid that .html extension): http://localhost:8080/swagger-ui/

Rebuild and restart the server. And your problem is solved!

Yes, you can. The trick here is that you have to get to the instance of the lambda that is passed to the registerMessage and then execute that expression and then you can verify the result.

For the purpose of a meaningful example I created this Handler class that contains the dispatchMessage that you want to test:

public class Handler {

    private Dispatcher dispatcher = new Dispatcher();

    public void dispatchMessage(MessageHandler handler, String argument1, String argument2, Long argument3) {

        handler.registerMessage(() -> {
            dispatcher.dispatch(argument1,
                    argument2,
                    argument3);
        });

    }

    interface MessageHandler {
        void registerMessage(Runnable run);
    }

    static class Dispatcher {
        void dispatch(String a, String b, long c){
            // Do dispatch
        }
    }
}

What you have to remember is that a lambda expression is just a short hand form to pass a function to a method. In this example the function is the run method of a Runnable. Therefore the method registerMessage of the interface for MessageHandler takes a Runnable as it's argument. I also included an implementation for the Dispatcher, which is called from within registerMessage. The test for this looks like this:

@RunWith(MockitoJUnitRunner.class)
public class HandlerTest {
    @Mock
    private Dispatcher dispatcher;
    @InjectMocks
    private Handler classUnderTest;
    @Captor
    private ArgumentCaptor<Runnable> registerMessageLambdaCaptor;

    @Test
    public void shouldCallDispatchMethod() {
        final String a = "foo";
        final String b = "bar";
        final long c = 42L;

        MessageHandler handler = mock(MessageHandler.class);

        classUnderTest.dispatchMessage(handler, a, b, c);

        verify(handler).registerMessage(registerMessageLambdaCaptor.capture());

        Runnable lambda = registerMessageLambdaCaptor.getValue();

        lambda.run();

        verify(dispatcher).dispatch(a, b, c);
    }
}

There is an ArgumentCaptor for the lambda expression which we use in the first verification of the registerMessage. After that verification we can retrieve the lambda expression from the captor. The type of the lambda expression is Runnable, as defined in the MessageHandler interface. Hence we can call the run method on it and then verify that the dispatch method on the Dispatcher was called with all the appropriate arguments.

Just use the org.joda.time.DateTimeUtils#setCurrentMillisFixed method of JodaTime which was designed to fix new DateTime() to a different time than the current time. To return to the normal time use org.joda.time.DateTimeUtils#setCurrentMillisSystem afterwards. No mocking needed.

@Test
public void test() {
DateTimeUtils.setCurrentMillisFixed(10L);
// .. your code
}

@After
public void cleanup() {
// Make sure to cleanup afterwards
DateTimeUtils.setCurrentMillisSystem()
}

PowerMockito.doAnswer(new Answer<Void>() {
    /* ... */
}).when(Connector.newConnection(Mockito.any(ConnectorConfig.class)));

Your when is the problem. In normal Mockito, using any doAnswer/doReturn/etc call, you have to place the call you're stubbing outside of the call to when, like so:

Mockito.doAnswer(new Answer<Void>() {
    /* ... */
}).when(yourMock).callVoidMethod();
//            ^^^^^^

PowerMockito further requires that calls to static methods happen in the next statement, like so:

PowerMockito.doAnswer(new Answer<Void>() {
    /* ... */
}).when(Connector.class); Connector.newConnection(/*...*/);
//                    ^^^^^^

Note that from 2009 (~1.3.x) to 2013 (~1.5.x), the docs were actually inconsistent, alluding to a zero-arg when despite all signatures requiring at least a class literal.

Obligatory PSA: It's generally a good idea to avoid mocking types you don't own, though opinions may vary on that one.

If I understood the task correctly it could be like this

static boolean isClosed;

public void run() {
    InputStream inputStream = null;
    try {
        inputStream = new FileInputStream(file) {
            @Override
            public void close() throws IOException {
                isClosed = true;
                super.close();
            }
        };
        // more stuff here

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

Note that documentToPojo takes a Class as its second argument. any(Foo.class) returns an argument of type Foo, not of type Class<Foo>, whereas eq(WorkItemDTO.class) should return a Class<WorkItemDTO> as expected. I'd do it this way:

when(mongoUtil.documentToPojo(
    Mockito.any(Document.class),
    Mockito.eq(WorkItemDTO.class))).thenReturn(...);