Mocking Static Blocks in Java

Solution 1:

PowerMock is another mock framework that extends EasyMock and Mockito. With PowerMock you can easily remove unwanted behavior from a class, for example a static initializer. In your example you simply add the following annotations to your JUnit test case:

@RunWith(PowerMockRunner.class)
@SuppressStaticInitializationFor("some.package.ClassWithStaticInit")

PowerMock does not use a Java agent and therefore does not require modification of the JVM startup parameters. You simple add the jar file and the above annotations.

Solution 2:

Occasionally, I find static initilizers in classes that my code depends on. If I cannot refactor the code, I use PowerMock's @SuppressStaticInitializationFor annotation to suppress the static initializer:

@RunWith(PowerMockRunner.class)
@SuppressStaticInitializationFor("com.example.ClassWithStaticInit")
public class ClassWithStaticInitTest {

    ClassWithStaticInit tested;

    @Before
    public void setUp() {
        tested = new ClassWithStaticInit();
    }

    @Test
    public void testSuppressStaticInitializer() {
        asserNotNull(tested);
    }

    // more tests...
}

Read more about suppressing unwanted behaviour.

Disclaimer: PowerMock is an open source project developed by two colleagues of mine.