How to use should_throw_mock_exception_without_stacktrace method of org.mockito.internal.stubbing.answers.AbstractThrowsExceptionTest class

Use when(spy.myMethod()).thenReturn(null). This will prevent the spy from invoking the wrapped instance. You have to tell Mockito what to return for a method that returns something. The default behavior for a mock is to return null. The default behavior for a spy is to call the wrapped object. When you stub a method in a spy it prevents the call to the wrapped object and executes the specified behavior.

Per documents of Spy, you could also do doReturn(null).when(spy).myMethod();

Finally I got some times to investigate and I made it. Here is my solution.

@RunWith(PowerMockRunner.class)
@PowerMockRunnerDelegate(VertxUnitRunner.class)
@PrepareForTest({ MongoClient.class })
public class PersistenceTest {

private MongoClient mongo;
private Vertx vertx;

@Before
public void initSingleTest(TestContext ctx) throws Exception {
  vertx = Vertx.vertx();
  mongo = Mockito.mock(MongoClient.class);
  PowerMockito.mockStatic(MongoClient.class);
  PowerMockito.when(MongoClient.createShared(Mockito.any(), Mockito.any())).thenReturn(mongo);
  vertx.deployVerticle(Persistence.class, new DeploymentOptions(), ctx.asyncAssertSuccess());
}

@SuppressWarnings("unchecked")
@Test
public void loadSomeDocs(TestContext ctx) {
  Doc expected = new Doc();
  expected.setName("report");
  expected.setPreview("loremipsum");
  Message<JsonObject> msg = Mockito.mock(Message.class);
  Mockito.when(msg.body()).thenReturn(JsonObject.mapFrom(expected));
  JsonObject result = new JsonObject().put("name", "report").put("preview", "loremipsum");
  AsyncResult<JsonObject> asyncResult = Mockito.mock(AsyncResult.class);
  Mockito.when(asyncResult.succeeded()).thenReturn(true);
  Mockito.when(asyncResult.result()).thenReturn(result);
  Mockito.doAnswer(new Answer<AsyncResult<JsonObject>>() {
    @Override
    public AsyncResult<JsonObject> answer(InvocationOnMock arg0) throws Throwable {
    ((Handler<AsyncResult<JsonObject>>) arg0.getArgument(3)).handle(asyncResult);
    return null;
    }
  }).when(mongo).findOne(Mockito.any(), Mockito.any(), Mockito.any(), Mockito.any());
  Async async = ctx.async();
  vertx.eventBus().send("persistence", new JsonObject(), msgh -> {
    if (msgh.failed()) {
    System.out.println(msgh.cause().getMessage());
    }
    ctx.assertTrue(msgh.succeeded());
    ctx.assertEquals(expected, Json.decodeValue(msgh.result().body().toString(), Doc.class));
    async.complete();
  });
  async.await();
  }
}

Use Powemockito to mock the MongoClient.createShared static method, so you'll have your mock when verticle starts. Mocking async handler is a bit of code to write. As you can see mocking start at Message<JsonObject> msg = Mockito.mock(Message.class); and ends at Mockito.doAnswer(new Answer.... In the Answer's method pick the handler param and force it to handle your async result then you're done.

The argThat return type is not being inferred for some reason. Try explicitly casting as shown below:

 Mockito.verify(foo).bar((Map<String, String>) argThat(Matchers.hasEntry("paramName", "paramValue")));

The testHasEntryCast() can be fixed as shown below. Notice that cast (Map<String, ?>) is to argThat return type:

@Test
public void testHasEntryCast() {
    Service mockService = mock(Service.class);
    Foo foo = new Foo(mockService);

    foo.bar();

    verify(mockService).activate((Map<String, ?>)  argThat(hasEntry("paramName", "paramValue")));
}

Use an Answer to check the value of the argument when the method is called. You can either throw an AssertionError within the Answer if the value is wrong, or you can store the value, and do your assertion at the end.

It's a bug: https://github.com/spring-projects/spring-boot/issues/6541

The fix is in spring-data 1.0.2-SNAPSHOT and 2.0.3-SNAPSHOT : https://github.com/arangodb/spring-data/issues/14#issuecomment-374141173

If you aren't using these version, you can work around it by declaring the mock with its name:

@MockBean(name="myMongoRepository")
private MyMongoRepository repository;

In response to your comment

From Spring's doc:

For convenience, tests that need to make REST calls to the started server can additionally @Autowire a TestRestTemplate which will resolve relative links to the running server.

Reading this, I think you need to declare @SpringBootTest with a web environment:

@SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT)

If your spring boot doesn't start the web environment, then what is the need for TestRestTemplate. Thus, I guess spring does not even make it available.

I am currently in the same boat as you and my reasoning was as follows: Creating a dummy JSON-response is like mocking an object and controlling it using Mockito.when. You would need to change anything in the when().thenReturn() call when you changed some inner parsing or you expect different results. This is the same with a JSON-response where calls are changed and object representations are altered.

Therefore my guess would be that this is fine. Reading various articles about testing REST API's, the general concensus is that creating dummy JSON-responses is good practice. Best practice would be to (from time to time) download the real JSON-response and insert this as the mocked response. This way you can keep your tests up-to-date with the external party, while the tests can run without internet requests.

Edit as requested:

• Ruby - Stubbing external services,

• Python - Testing a successful call

• JavaScript - An example of AJAX testing

• Python - Lastly a Google tutorial about mocking

This stub is wrong :

doNothing().when(mockObject.methodToStub(captor.capture())); // wrong

methodToStub(...) must be outside the when if using this API style (it should only contain the mock) :

doNothing().when(mockObject).methodToStub(captor.capture()); // correct

Tho remarks however :

1. doNothing is the default for void methods for a mock.
2. You can use the BDDMockito aliases that enables your code to be real à la Behavior Driven Development

Just to complete the picture:

The latest version of Mockito 2 very well supports mocking of final classes. But you have to explicitly enable this new experimental feature first!

( see here on how to do that - it boils down to add a file mockito-extensions/org.mockito.plugins.MockMaker to your classpath, containing the value mock-maker-inline )

But of course: you only mock something if you have to. Your desire to mock Enum instances is most likely driven by either not understanding that - or because you created hard to test code here. In that sense the real answer would be to look into ways that avoid this kind of mocking in the first place.

Injecting mock bean with @MockBean annotation works if your dependency in ClassUnderTest is represented by interface. Let's say Dependency is a simple interface like:

package di.failure.example;

public interface Dependency {
    void run();
}

Your application may provide an implementation for this interface called DependencyImpl:

package di.failure.example;

import javax.inject.Singleton;

@Singleton
public class DependencyImpl implements Dependency {
    @Override
    public void run() {
        throw new RuntimeException("I don't want this to load!");
    }
}

Now, for test purpose you can define a mock that replaces DependencyImpl:

package di.failure.example;

import io.micronaut.test.annotation.MicronautTest;
import io.micronaut.test.annotation.MockBean;
import org.junit.jupiter.api.Test;

import javax.inject.Inject;

import static org.mockito.Mockito.mock;

@MicronautTest
public class ClassUnderTestTest {

    @Inject
    ClassUnderTest classUnderTest;

    @Test
    public void test() {
        classUnderTest.run();
    }

    @MockBean(DependencyImpl.class)
    public Dependency dependency() {
        return mock(Dependency.class);
    }

}

This test executes and the mock returned by dependency() method is used in place of DependencyImpl.

Using @Replaces annotation

As Sergio mentioned in the comments section you can replace class based bean dependency using @Replaces annotation. Consider following example:

package di.failure.example;

import io.micronaut.context.annotation.Replaces;
import io.micronaut.test.annotation.MicronautTest;
import org.junit.jupiter.api.Test;

import javax.inject.Inject;
import javax.inject.Singleton;

@MicronautTest
public class ClassUnderTestTest {

    @Inject
    ClassUnderTest classUnderTest;

    @Test
    public void test() {
        classUnderTest.run();
    }

    @Replaces(Dependency.class)
    @Singleton
    public static class MockDependency extends Dependency {

        public MockDependency() {
            System.out.println("MockDependency.<init>");
        }

        @Override
        void run() {
            System.out.println("Does not throw any exception...");
        }
    }
}

In this example we have defined a class MockDependency and we instruct Micronaut's DI mechanism to replace Dependency bean with MockDependency. However, there is one important thing we need to remember about - because our MockDependency extends Dependency class, parent construct gets invoked. The example you have shown in the question won't work in this case, because Dependency.<init> throws RuntimeException and the test fails. In this modified example I have used class like this one:

package di.failure.example;

import javax.inject.Singleton;

@Singleton
public class Dependency {

    public Dependency() {
        System.out.println("Dependency.<init>");
    }

    void run() {
        throw new RuntimeException("I don't want this to load!");
    }
}

When I run the test it passes and I see following console output:

Dependency.<init>
MockDependency.<init>
Does not throw any exception...

The main difference comparing to @MockBean is that in case of @Replaces you are using a concrete class object. As a workaround (if we really need a Mockito mock object) is to create a mock internally and delegate calls to this object, something like this:

@Replaces(Dependency.class)
@Singleton
public class MockDependency extends Dependency {

    private final Dependency delegate;

    public MockDependency() {
        this.delegate = mock(Dependency.class);
    }

    @Override
    void run() {
        delegate.run();
    }
}