PowerMockito verifyNew and verifyPrivate are mutually exclusive? - spring

Question

I have a class like this
#Component
public class TestClass {
public void testMethod(){
FinalClass f = new FinalClass("string");
somePrivateMethod(f.getSomeString());
}
private void somePrivateMethod(String s){
}
}
As you can see it has a public method and private method. In public method it is instantiating an instance of FinalClass, which is a class in some third party library and it is final. Lets say it is like this
public final class FinalClass {
private final String someString;
public FinalClass(final String s) {
someString = s;
}
public String getSomeString() {
return someString;
}
}
And Now I am writing unit test for my test class. Since I have to verify final classes and private methods, I am using powermockito. And this is how my test class looks like
#RunWith(PowerMockRunner.class)
#PrepareForTest({TestClass.class, FinalClass.class})
public class TestClassTest {
private TestClass testClass;
private FinalClass finalClass;
#Before
public void setUp() {
finalClass = PowerMockito.mock(FinalClass.class);
testClass = spy(new TestClass());
}
#Test
public void testSomething() throws Exception {
whenNew(FinalClass.class).withAnyArguments().thenReturn(finalClass);
testClass.testMethod();
verifyNew(FinalClass.class);
//verifyPrivate(testClass).invoke("testMethod");
}
}
It works fine. But the problem is the last two statements verifyNew and verifyPrivate are working mutually exclusively. I mean when I comment one of those(doesn't matter which), the test passes. But when both are enabled, the test fails
Does anyone have any idea why this is happening?