What are the main differences between PowerMock's whitebox and Mockito's whitebox

Origin and Availability

- Mockito's Whitebox: This was an internal class within Mockito that allowed users to set internal states of objects. However, it was removed from Mockito 2.x due to concerns about promoting bad testing practices and because it was not intended for public use[11]. Users who relied on it were encouraged to switch to alternatives like PowerMock's Whitebox or implement their own reflection utilities[3].

- PowerMock's Whitebox: This is part of the PowerMock library, which extends Mockito's capabilities by allowing the mocking of private, static, and final methods, among other features[5]. PowerMock's Whitebox provides a simplified reflection utility intended for tests, enabling access to private members and invocation of private methods[2][6].

Functionality

- Mockito's Whitebox (Historical): Before its removal, Mockito's Whitebox allowed users to set internal states of objects using methods like `setInternalState`. This was useful for injecting mocks into classes without public setters.

- PowerMock's Whitebox: Offers a broader set of functionalities, including:
- Accessing Private Members: Methods like `getInternalState` allow retrieval of private field values.
- Invoking Private Methods: The `invokeMethod` method can call private methods, including static ones[4][10].
- Setting Private Fields: While not explicitly documented, PowerMock's Whitebox can be used to set private fields through reflection, though this is not its primary purpose.

Usage Context

- Mockito's Whitebox: Since it's no longer available in Mockito 2.x, users are advised to use alternatives like PowerMock's Whitebox or Spring's `ReflectionTestUtils` if applicable[1][3].

- PowerMock's Whitebox: Typically used in scenarios where direct access to private members or methods is necessary, often in legacy code or when testing complex logic that cannot be easily refactored. However, it's generally recommended to avoid using such utilities unless absolutely necessary, as they can bypass encapsulation and lead to brittle tests[10].

In summary, while both Whitebox utilities serve similar purposes, PowerMock's version is more comprehensive and widely available, whereas Mockito's version was removed due to concerns about testing practices. PowerMock's Whitebox is a powerful tool for accessing and manipulating internal class states but should be used judiciously.