How do I mock static methods in a class with easymock?

Question

Suppose I have a class like so:

public class StaticDude{
    public static Object getGroove() {
        // ... some complex logic which returns an object
    };
}

How do I mock the static method call using easy mock? StaticDude.getGroove().

I am using easy mock 3.0

Solution 1

Not sure how to with pure EasyMock, but consider using the PowerMock extensions to EasyMock.

It has a lot of cool functions for doing just what you need - https://github.com/jayway/powermock/wiki/MockStatic

Solution 2

Easymock is a testing framework for "for interfaces (and objects through the class extension)" so you can mock a class without an interface. Consider creating an interfaced object with an accessor for your static class and then mock that acessor instead.

EDIT: Btw, I wouldn't recommend doing static classes. It is better to have everything interfaced if you are doing TDD.

Solution 3

Just in Case PowerMock is unavailable for any reason:

You could move the static call to a method, override this method in the instantiation of the tested class in the test class, create a local interface in the test class and use its method in the overidden method:

private interface IMocker 
{
    boolean doSomething();
}

IMocker imocker = EasyMock.createMock(IMocker.class);

...

@Override
void doSomething()
{
     imocker.doSomething();
}

...

EasyMock.expect(imocker.doSomething()).andReturn(true);

Solution 4

Generally speaking, it is not possible to mock a static method without using some sort of accessor, which seems to defeat the purpose of using a static method. It can be quite frustrating.

There is one tool that I know of called "TypeMock Isolator" which uses some sort of Satanic Magic to mock static methods, but that tool is quite expensive.

The problem is, I know of no way to override a static method. You can't declare it virtual. you can't include it in an interface.

Sorry to be a negative nelly.

Solution 5

Adding an exemple on how to implements static mock along regular mock of injected classes with EasyMock / PowerMock, since the linked exemple only shows static mock.

And with the PowerMockRunner the @Mock services are not wired on the @TestSubject service to test.

Let say we have a service we want to test, ServiceOne :

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class ServiceOne {

    @Autowired
    private ServiceTwo serviceTwo;

    public String methodToTest() {
        String returnServ2 = serviceTwo.methodToMock();
        return ServiceUtils.addPlus(returnServ2);
    }
}

Which calls another service that we will want to mock, ServiceTwo :

import org.springframework.stereotype.Service;

@Service
public class ServiceTwo {

    public String methodToMock() {
        return "ServiceTwoReturn";
    }
}

And which calls a final class static method, ServiceUtils :

public final class ServiceUtils {

    public static String addPlus(String pParam) {
        return "+" + pParam;
    }
}

When calling ServiceOne.methodToTest() we get "+ServiceTwoReturn" as a return.

---

Junit Test with EasyMock, mocking only the injected ServiceTwo Spring service :

import static org.easymock.EasyMock.expect;
import static org.easymock.EasyMock.replay;
import static org.easymock.EasyMock.verify;
import static org.junit.Assert.assertEquals;

import org.easymock.EasyMockRunner;
import org.easymock.Mock;
import org.easymock.TestSubject;
import org.junit.Test;
import org.junit.runner.RunWith;

@RunWith(EasyMockRunner.class)
public class ExempleTest {

    @TestSubject
    private ServiceOne serviceToTest = new ServiceOne();

    @Mock
    private ServiceTwo serviceMocked;

    @Test
    public void testMethodToTest() {
        String mockedReturn = "return2";

        expect(serviceMocked.methodToMock()).andReturn(mockedReturn);
        replay(serviceMocked);

        String result = serviceToTest.methodToTest();

        verify(serviceMocked);

        assertEquals("+" + mockedReturn, result);
    }
}

---

Junit Test with EasyMock & PowerMock, mocking the injected ServiceTwo Spring service but also the final class and its Static method :

import static org.easymock.EasyMock.expect;
import static org.junit.Assert.assertEquals;
import static org.powermock.api.easymock.PowerMock.createMock;
import static org.powermock.api.easymock.PowerMock.mockStatic;
import static org.powermock.reflect.Whitebox.setInternalState;

import org.easymock.Mock;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.api.easymock.PowerMock;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(ServiceUtils.class)
public class ExempleTest {

    private ServiceOne serviceToTest;

    private ServiceTwo serviceMocked;

    @Before
    public void setUp() {
        serviceToTest = new ServiceOne();
        serviceMocked = createMock(ServiceTwo.class);
        // This will wire the serviced mocked into the service to test
        setInternalState(serviceToTest, serviceMocked);
        mockStatic(ServiceUtils.class);
    }

    @Test
    public void testMethodToTest() {
        String mockedReturn = "return2";
        String mockedStaticReturn = "returnStatic";

        expect(serviceMocked.methodToMock()).andReturn(mockedReturn);
        expect(ServiceUtils.addPlus(mockedReturn)).andReturn(mockedStaticReturn);
        PowerMock.replayAll();

        String result = serviceToTest.methodToTest();

        PowerMock.verifyAll();

        assertEquals(mockedStaticReturn, result);
    }
}

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Comments

[Chris311]

This way one has to change the productive code just for the sake of a test.