How to use warnForVM method of org.mockito.internal.util.Platform class

UPDATE: My answer is quite old. There is a built-in method in Mockito now to insert the delay directly: AnswersWithDelay. See Bogdan's response for more details.

There is already a CallsRealMethods Answer that you can extend and decorate with your delay:

public class CallsRealMethodsWithDelay extends CallsRealMethods {

    private final long delay;

    public CallsRealMethodsWithDelay(long delay) {
        this.delay = delay;
    }

    public Object answer(InvocationOnMock invocation) throws Throwable {
        Thread.sleep(delay);
        return super.answer(invocation);
    }

}

And then use it like that:

MyObject foobar = Mockito.spy(new MyObject(param1, param2, param3));
Mockito.doAnswer(new CallsRealMethodsWithDelay(2000))
           .when(foobar).myRealMethodName();

You can of course also use a static method to make everything even more beautiful:

public static Stubber doAnswerWithRealMethodAndDelay(long delay) {
    return Mockito.doAnswer(new CallsRealMethodsWithDelay(delay));
}

And use it like:

doAnswerWithRealMethodAndDelay(2000)
           .when(foobar).myRealMethodName();

To answer your second question first. If you're using JUnit 4, you can annotate your test with

@Test(expected=MyException.class)

to assert that an exception has occured. And to "mock" an exception with mockito, use

when(myMock.doSomething()).thenThrow(new MyException());

You can use MockingDetails and either printInvocations or getInvocations to inspect the interactions belonging to a mock. However, this will not produce a list of invocations belonging to multiple mocks in the order that happened: just interactions with each individual mock.

Code snippet, as contributed by elhefe and Anand Rockzz:

import static org.mockito.Mockito.mockingDetails;

System.out.println(mockingDetails(mock).printInvocations());
/* or */
System.out.println(mockingDetails(mock).getInvocations());

Acknowledging your reluctance and caveats in the comments, I would say that this is a technique that does more to lock in your current implementation than to analyze your real constraints and prevent regressions. Furthermore, if your algorithm has a lot of interactions with direct collaborators, that might be an indication that the algorithm should be refactored.

If the system is untested or undocumented legacy code, this might be a practical way to programmatically generate a regression test or analysis--a temporary starting point for more-informed regression testing--but in your shoes I would instead start by documenting the contract of each component and then writing a test that confirms those interactions and constraints. Mockito recommendations (as intimated through this article by Mockito's original developer) tend toward adding stubs until tests pass and adding verifications/counts only where there are expensive or non-idempotent side effects.

Not possible through mockito. From their wiki

Why Mockito doesn't mock private methods?

Firstly, we are not dogmatic about mocking private methods. We just don't care about private methods because from the standpoint of testing private methods don't exist. Here are a couple of reasons Mockito doesn't mock private methods:

It requires hacking of classloaders that is never bullet proof and it changes the api (you must use custom test runner, annotate the class, etc.).

It is very easy to work around - just change the visibility of method from private to package-protected (or protected).

It requires me to spend time implementing & maintaining it. And it does not make sense given point #2 and a fact that it is already implemented in different tool (powermock).

Finally... Mocking private methods is a hint that there is something wrong with OO understanding. In OO you want objects (or roles) to collaborate, not methods. Forget about pascal & procedural code. Think in objects.

From the docs:

Sometimes we need to stub with different return value/exception for the same method call. Typical use case could be mocking iterators. Original version of Mockito did not have this feature to promote simple mocking. For example, instead of iterators one could use Iterable or simply collections. Those offer natural ways of stubbing (e.g. using real collections). In rare scenarios stubbing consecutive calls could be useful, though:

when(mock.someMethod("some arg"))
   .thenThrow(new RuntimeException())
  .thenReturn("foo");

//First call: throws runtime exception:
mock.someMethod("some arg");

//Second call: prints "foo"
System.out.println(mock.someMethod("some arg"));

So in your case, you'd want:

when(myMock.doTheCall())
   .thenReturn("You failed")
   .thenReturn("Success");

Dependency Injection

If you inject the Bar instance, or a factory that is used for creating the Bar instance (or one of the other 483 ways of doing this), you'd have the access necessary to do perform the test.

Factory Example:

Given a Foo class written like this:

public class Foo {
  private BarFactory barFactory;

  public Foo(BarFactory factory) {
    this.barFactory = factory;
  }

  public void foo() {
    Bar bar = this.barFactory.createBar();
    bar.someMethod();
  }
}

in your test method you can inject a BarFactory like this:

@Test
public void testDoFoo() {
  Bar bar = mock(Bar.class);
  BarFactory myFactory = new BarFactory() {
    public Bar createBar() { return bar;}
  };
  
  Foo foo = new Foo(myFactory);
  foo.foo();

  verify(bar, times(1)).someMethod();
}

Bonus: This is an example of how TDD(Test Driven Development) can drive the design of your code.

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.

Mockito, till version 1.8.5, had a bug in the case of polymorphic dispatch. It was fixed and is available in the first release candidate of the version 1.9.0. See issue 200.

So how does it happen in your code base. Note you are mocking these two classes

nodeAutoIndexer = (AutoIndexer<Node>) mock(AutoIndexer.class);
relAutoIndexer = mock(RelationshipAutoIndexer.class);

AutoIndexer happen to be a generic parent interface, in this interface there is this method ReadableIndex<T> getAutoIndex(). RelationshipAutoIndexer is a subtype of the AutoInexer where the generic part is fixed to Relationship, and override the getAutoIndex() method to return the covariant type ReadableRelationshipIndex.

See AutoIndexer and RelationshipIndexer.

Well, in your calling code you have these lines:

AutoIndexer<Node> nodeAutoIndexer = this.graphDb.index().getNodeAutoIndexer();
AutoIndexer<Relationship> relAutoIndexer = this.graphDb.index().getRelationshipAutoIndexer();
this.nodeIndex = nodeAutoIndexer.getAutoIndex();
this.relIndex = relAutoIndexer.getAutoIndex();

Both nodeAutoIndex in your production code and the mock nodeAutoIndexer in your test code have a reference of type AutoIndexer<Node>, so there's no problem regarding polymorphic dispatch. However relAutoIndex in your production code is referenced by the type AutoIndexer<Relationship> and the mock relAutoIndexer in your test code is referenced by the type RelationshipAutoIndexer, so the wrong call is registered on the mock and then fails verification.

Your solution is either to upgrade the mockito version; the 1.9.0 RC1 is very stable and a final release should be coming your way. Or you can migrate your reference type (in your production code) from :

AutoIndexer<Relationship> relAutoIndexer = this.graphDb.index().getRelationshipAutoIndexer();

to :

RelationshipAutoIndexer relAutoIndexer = this.graphDb.index().getRelationshipAutoIndexer();

A few other remarks.

• You don't actually need to write an after method here as JUnit creates a new instance on each method run, so your method just adds code that will be done anyway. Note this isn't the case with TestNG.

• Instead of creating your mocks in the before method, you might want to use Mockito annotations. Don't forget the runner.

For example :

@RunWith(MockitoJUnitRunner.class)
public class YourTest {
    @Mock SomeType someTypeMock;
    // ...
}

• The stubbing code is a bit ugly for several reasons.

  • Your should write consistent stubs.

Why not write this in a cleaner way; for example referencing indexManager in both case :

IndexManager indexManager = mock(IndexManager.class);
when(graphDb.index()).thenReturn(indexManager);
when(indexManager.getNodeAutoIndexer()).thenReturn(nodeAutoIndexer);
when(indexManager.getRelationshipAutoIndexer()).thenReturn(relAutoIndexer);

Or don't reference it at all

IndexManager indexManager = mock(IndexManager.class);
when(graphDb.index()).thenReturn(indexManager);
when(graphDb.index().getNodeAutoIndexer()).thenReturn(nodeAutoIndexer);
when(graphDb.index().getRelationshipAutoIndexer()).thenReturn(relAutoIndexer);

Also having a mock that returns a mock is usually a sign of design smell. You are breaking the law of Demeter, and breaking it means you will experience difficult testing, bad maintainability, and difficult evolution. When I say that you could hear me whisper also (without the syllogisms) : it will cost you money. Don't write legacy code! If you are practicing TDD or BDD, you will identify these issues at design time for your own code, which is great to prevent them.

• However if you are dealing with legacy code, you can use this deep stubs syntax :

Using the static methods you could write this

GraphDatabaseService graphdb = mock(GraphDatabaseService.class, RETURNS_DEEP_STUBS);

Or using the annotation you could write this :

@Mock(answer = RETURNS_DEEP_STUBS) GraphDatabaseService graphdb;

And the stubbing :

when(graphDb.index().getNodeAutoIndexer()).thenReturn(nodeAutoIndexer);
when(graphDb.index().getRelationshipAutoIndexer()).thenReturn(relAutoIndexer);

I think what you are trying to test is aspect weaving and pointcut matching. Please note that that would be an integration rather than a unit test. If you really want to unit test your aspect logic and because you have tagged the question by "mockito" anyway, I suggest you do just that: Write a unit test and mock the aspect's joinpoint and maybe its other parameters, if any. Here is a slightly more complex example with some intra-aspect logic:

Java class to be targeted by aspect:

package de.scrum_master.app;

public class Application {
    public static void main(String[] args) {
        new Application().doSomething(11);
        new Application().doSomething(-22);
        new Application().doSomething(333);
    }

    public void doSomething(int number) {
        System.out.println("Doing something with number " + number);
    }
}

Aspect under test:

package de.scrum_master.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;

@Aspect
public class SampleAspect {
    @Around("execution(* doSomething(int)) && args(number)")
    public Object intercept(final ProceedingJoinPoint thisJoinPoint, int number) throws Throwable {
        System.out.println(thisJoinPoint + " -> " + number);
        if (number < 0)
            return thisJoinPoint.proceed(new Object[] { -number });
        if (number > 99)
            throw new RuntimeException("oops");
        return thisJoinPoint.proceed();
    }
}

Console log when running Application.main(..):

As you can see, the aspect passes on 11, negates -22 and throws an exception for 333:

execution(void de.scrum_master.app.Application.doSomething(int)) -> 11
Doing something with number 11
execution(void de.scrum_master.app.Application.doSomething(int)) -> -22
Doing something with number 22
execution(void de.scrum_master.app.Application.doSomething(int)) -> 333
Exception in thread "main" java.lang.RuntimeException: oops
    at de.scrum_master.aspect.SampleAspect.intercept(SampleAspect.aj:15)
    at de.scrum_master.app.Application.doSomething(Application.java:10)
    at de.scrum_master.app.Application.main(Application.java:7)

Unit test for aspect:

Now we really want to verify that the aspect does what it should and cover all execution paths:

package de.scrum_master.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.junit.Rule;
import org.junit.Test;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnit;
import org.mockito.junit.MockitoRule;

import static org.mockito.Mockito.*;

public class SampleAspectTest {
    @Rule
    public MockitoRule mockitoRule = MockitoJUnit.rule();

    @Mock
    private ProceedingJoinPoint proceedingJoinPoint;

    private SampleAspect sampleAspect = new SampleAspect();

    @Test
    public void testPositiveSmallNumber() throws Throwable {
        sampleAspect.intercept(proceedingJoinPoint, 11);
        // 'proceed()' is called exactly once
        verify(proceedingJoinPoint, times(1)).proceed();
        // 'proceed(Object[])' is never called
        verify(proceedingJoinPoint, never()).proceed(null);
    }

    @Test
    public void testNegativeNumber() throws Throwable {
        sampleAspect.intercept(proceedingJoinPoint, -22);
        // 'proceed()' is never called
        verify(proceedingJoinPoint, never()).proceed();
        // 'proceed(Object[])' is called exactly once
        verify(proceedingJoinPoint, times(1)).proceed(new Object[] { 22 });
    }

    @Test(expected = RuntimeException.class)
    public void testPositiveLargeNumber() throws Throwable {
        sampleAspect.intercept(proceedingJoinPoint, 333);
    }
}

Now run this simple JUnit + Mockito test in order to test the aspect logic in isolation, not the wiring/weaving logic. For the latter you would need another type of test.

P.S.: Only for you I used JUnit and Mockito. Usually I just use Spock and its built-in mocking capabilities. ;-)