SuppressStaticInitializationFor

If you are working with classes which have static initializers such as:

package com.example;

public class ClassWithStaticInitializer {
        private static Handler mHandler = new Handler();
}

As mHandler belongs to ClassWithStaticInitializer.class not instance of ClassWithStaticInitializer, JVM will initialize this mHandler as soon as execution starts, thus we will not get a chance to mock it with whenNew(). In this case, we can suppress its initialization and later set its value with Whitebox.

Here is an example to suppress mHandler in ClassWithStaticInitializer.class:

@RunWith(PowerMockRunner.class)
@SuppressStaticInitializationFor({
        "com.example.ClassWithStaticInitializer"
})
public class ClassWithStaticInitializerTest {
        // now when we call
        @Before
        public void setup throws Exception {
                // At this stage, ClassWithStaticInitializer.mHandler will be null
                Whitebox.setInternalState(ClassWithStaticInitializer.class, "mHandler", mckHandler);
        }
}

tip: if you see any error with StackTrace containing similar looking line com.examlpe.ExampleClass.<clinit>. It means there is an static initializer, just add com.examlpe.ExampleClass in your SuppressStaticInitializationFor annotation.