Can I use @InjectMocks to mock private methods

Mockito has some limitations when it comes to mocking private methods:

1. Mocking Private Methods Directly: Mockito cannot directly mock private methods. Private methods are not accessible from outside the class, so Mockito has no way to intercept and override their behavior.

2. Mocking Through Spies: Mockito can mock private methods indirectly by using the `spy()` method. When you create a spy, Mockito can intercept and override the behavior of both public and private methods.

java
   MyClass myClass = Mockito.spy(new MyClass());
   when(myClass.privateMethod()).thenReturn("mocked value");
   

In this example, Mockito can mock the `privateMethod()` by creating a spy on the `MyClass` instance.

3. Mocking Through PowerMock: If you need to directly mock private methods, you can use a third-party library like PowerMock, which extends Mockito's capabilities. PowerMock uses bytecode instrumentation to enable mocking of private, static, and final methods.

java
   @RunWith(PowerMockRunner.class)
   @PrepareForTest(MyClass.class)
   public class MyClassTest {
       @Test
       public void testPrivateMethod() {
           MyClass myClass = PowerMockito.spy(new MyClass());
           PowerMockito.when(myClass, "privateMethod").thenReturn("mocked value");
           // Test the behavior
       }
   }
   

In this example, we use PowerMock's `PowerMockito` class to mock the private `privateMethod()` directly.

It's important to note that while PowerMock can be used to mock private methods, it's generally considered a more complex and heavyweight solution compared to Mockito. It's recommended to use Mockito's `spy()` method whenever possible, as it provides a more straightforward and maintainable approach to mocking private methods.

Additionally, if you find yourself needing to mock private methods frequently, it may be a sign that your class design could be improved, and you should consider refactoring your code to make it more testable.