1. One of NPE solutions for mock SomeClass someclass = mock(SomeClass.class,Mockito.RETURNS_DEEP_STUBS); 2. Assert Any Exceptions assertThrows(RunTimeException.class, ()->{ //logic code }); 3. Mock/Test private method @InjectMocks PrivateInClass privateInClass; ReflectionTestUtils.invokeMethod(privateInClass, “privateMethodName”, param1, param2, …); 4. Mock final class Add below file in test path …/test/resources/mockkito-extensions/org.mockito.plugins.MockMaker MockMaker content mock-maker-inline