How do I mock a static method call from a nother static method in the same class?

Question

I have a utilities class wherein one static method calls another. I want to mock the called method but not the target method. Does anyone have an example?

I've got:

@RunWith(PowerMockRunner.class)
@PrepareForTest({SubjectUnderTest.class})
public class SubjectUnderTestTest {
...
    SubjectUnderTest testTarget = PowerMockito.mock(SubjectUnderTest.class, Mockito.CALLS_REAL_METHODS);

Answer 1

Starting from the docs, with some minor tweaks, you can either mock or spy the static method, depending on what you need (spying seems a bit less verbose but has different syntax). You can find below a sample for both, based on PowerMockito 1.7.3 & Mockito 1.10.19.

Given the following simple class with the required 2 static methods:

public class ClassWithStaticMethods {

    public static String doSomething() {
        throw new UnsupportedOperationException("Nope!");
    }

    public static String callDoSomething() {
        return doSomething();
    }

}

You can do something like:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;
import static org.powermock.api.mockito.PowerMockito.*;

// prep for the magic show
@RunWith(PowerMockRunner.class)
@PrepareForTest(ClassWithStaticMethods.class)
public class ClassWithStaticMethodsTest {

    @Test
    public void shouldMockStaticMethod() {
        // enable static mocking
        mockStatic(ClassWithStaticMethods.class);

        // mock the desired method
        when(ClassWithStaticMethods.doSomething()).thenReturn("Did something!");

        // can't use Mockito.CALLS_REAL_METHODS, so work around it
        when(ClassWithStaticMethods.callDoSomething()).thenCallRealMethod();

        // validate results
        assertThat(ClassWithStaticMethods.callDoSomething(), is("Did something!"));
    }

    @Test
    public void shouldSpyStaticMethod() throws Exception {
        // enable static spying
        spy(ClassWithStaticMethods.class);

        // mock the desired method - pay attention to the different syntax
        doReturn("Did something!").when(ClassWithStaticMethods.class, "doSomething");

        // validate
        assertThat(ClassWithStaticMethods.callDoSomething(), is("Did something!"));
    }

}