How to use testEqualsWithDelta_NullExpected method of org.mockitousage.bugs.EqualsWithDeltaTest class

You can use PowerMockito along with Mockito to mock static methods:

@RunWith(PowerMockRunner.class)
@PrepareForTest(ServiceLoader.class)
public class PowerMockingStaticTest
{
    @Mock
    private ServiceLoader mockServiceLoader;

    @Before
    public void setUp()
    {
        PowerMockito.mockStatic(ServiceLoader.class);
        Mockito.when(ServiceLoader.load(Mockito.any(Class.class))).thenReturn(mockServiceLoader);
    }

    @Test
    public void test()
    {
        Assert.assertEquals(mockServiceLoader, ServiceLoader.load(Object.class));
    }
}

What you want to do is a combination of part of 1 and all of 2.

You need to use the PowerMockito.mockStatic to enable static mocking for all static methods of a class. This means make it possible to stub them using the when-thenReturn syntax.

But the 2-argument overload of mockStatic you are using supplies a default strategy for what Mockito/PowerMock should do when you call a method you haven't explicitly stubbed on the mock instance.

From the javadoc:

Creates class mock with a specified strategy for its answers to interactions. It's quite advanced feature and typically you don't need it to write decent tests. However it can be helpful when working with legacy systems. It is the default answer so it will be used only when you don't stub the method call.

The default default stubbing strategy is to just return null, 0 or false for object, number and boolean valued methods. By using the 2-arg overload, you're saying "No, no, no, by default use this Answer subclass' answer method to get a default value. It returns a Long, so if you have static methods which return something incompatible with Long, there is a problem.

Instead, use the 1-arg version of mockStatic to enable stubbing of static methods, then use when-thenReturn to specify what to do for a particular method. For example:

import static org.mockito.Mockito.*;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

class ClassWithStatics {
  public static String getString() {
    return "String";
  }

  public static int getInt() {
    return 1;
  }
}

@RunWith(PowerMockRunner.class)
@PrepareForTest(ClassWithStatics.class)
public class StubJustOneStatic {
  @Test
  public void test() {
    PowerMockito.mockStatic(ClassWithStatics.class);

    when(ClassWithStatics.getString()).thenReturn("Hello!");

    System.out.println("String: " + ClassWithStatics.getString());
    System.out.println("Int: " + ClassWithStatics.getInt());
  }
}

The String-valued static method is stubbed to return "Hello!", while the int-valued static method uses the default stubbing, returning 0.

I think you do need to cast it, but it shouldn't be too bad:

Foo<Bar> mockFoo = (Foo<Bar>) mock(Foo.class);
when(mockFoo.getValue()).thenReturn(new Bar());

Found it. The way I was doing it was correct. The only thing I missed was telling the mock object to call the original method when toString was called(). So it works like this:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ Foo.class })
public class FooTest
{
    @Test
    public void testToString() throws Exception
    {
        Foo foo = mock(Foo.class);
        when(foo.getBar()).thenReturn(42);
        when(foo.toString()).thenCallRealMethod();
        assertEquals("Bar: 42", foo.toString());
    }
}

When you want to use the @Mock annotation you should use the MockitoJUnitRunner

@RunWith(MockitoJUnitRunner.class)
public class MockitoTest {

    @Mock
    private IRoutingObjHttpClient routingClientMock;

    @Test
    public void testSendRoutingRequest() throws Exception {
        // ...
    }

}

See also this tutorial.

how about you create an anonymous exception of type JsonProcessingException

when(mapper.writeValueAsString(any(Object.class))).thenThrow(new JsonProcessingException("Error"){});

The {} braces does the trick. This is much better since it is not confusing to the reader of the test code.

With mockito 2.x, JDK 8 default methods are supported.

With mockito 1.x it's not possible,

Old answer

Unfortunately it's not yet possible (mockito 1.10.19), from the README.md on the github'page

JDK8 status

Mockito should work fine with JDK8 if you stay away from default methods (aka defender methods). Lambda usage may work just as good for Answers. We're unsure about every JDK8 features at the moment, like serializing a mock that uses a lambda. Error report and pull request are welcome though (contributing guide).

EDIT 1: defender methods and default methods are different names for the same thing.

I hope for a mockmaker replacement that will handle java 8 opcodes properly for such cases as some opcodes have a different semantic in Java 8.

EDIT 2: Updated the mockito readme, and this quote accordingly

Mockito supports changing the returned value; this support extends to PowerMockito. Just use OngoingStubbing.thenReturn(T value, T... values)

OngoingStubbing<T> thenReturn(T value, T... values)

Sets consecutive return values to be returned when the method is called.
E.g:

when(mock.someMethod()).thenReturn(1, 2, 3);

Last return value in the sequence (in example: 3) determines the behavior of further consecutive calls.

So, in this case, you would do:

PowerMockito.when(DBUtil.getCurrentCount()).thenReturn(100, 150);

Note: this answer assumes you already know how to mock static methods. If you do not, see this question.

You can use a Mock reponse or an actual response and then use when, e.g.:

Page<Company> companies = Mockito.mock(Page.class);
Mockito.when(companyRepository.findAllByIsActiveTrue(pageable)).thenReturn(companies);

Or, just instantiate the class:

List<Company> companies = new ArrayList<>();
Page<Company> pagedResponse = new PageImpl(companies);
Mockito.when(companyRepository.findAllByIsActiveTrue(pagedResponse)).thenReturn(pagedResponse);