Powermock of static class gives error: java.lang.NoClassDefFoundError: Could not initialize class XXX

Question

Problem

Could not initialize class ...

...javax.xml.transform.FactoryFinder (in our case).
In the article, where we found the solution, it was the class SessionFactory.

Class Under Test

We wanted to write a test for a utils class with static members. We got the error when trying to create a Mock of a class, which contained a new statement as an initialization of a static field.

public class ClassUnderTest{
    private static JavaType javaType =  new JavaType();
    // ...
}

Test Class

@RunWith(PowerMockRunner.class)
@PrepareForTest(ClassUnderTest.class)
public class TestForClassUnderTest {

    @Test
    public void testCase() {

        PowerMockito.mockStatic(ClassUnderTest.class);

score 3 · Answer 1 · answered Dec 03 '20 at 15:42

Solution

The solution was adding another class level annotation to the test class:

@SuppressStaticInitializationFor("com.example.package.util.ClassUnderTest")

Note, that you have to give the package path and no .class at the end. Unlike @PrepareFor.

Thanks to this article: http://www.gitshah.com/2010/06/how-to-suppress-static-initializers.html

Test Class with Solution

//...
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.core.classloader.annotations.SuppressStaticInitializationFor;

@RunWith(PowerMockRunner.class)
@PrepareForTest(ClassUnderTest.class)
@SuppressStaticInitializationFor("com.example.package.util.ClassUnderTest") // <-- this is it :)
public class TestForClassUnderTest {

  @Test
  public void testCase() {
    PowerMockito.mockStatic(ClassUnderTest.class);
    //...
  }
}