What causes a ClassFormatError while writing JUnit 4 tests with MockitoJUnitRunner?

"What leads to a ClassFormatError when writing JUnit 4 tests using MockitoJUnitRunner?"

A "ClassFormatError" while writing JUnit 4 tests with MockitoJUnitRunner can occur due to several reasons:

Incorrect Mockito Version: Ensure you are using a compatible version of Mockito with JUnit 4. Using a version of Mockito that is not compatible with JUnit 4 can lead to errors.

Deprecated MockitoJUnitRunner: If you are using a deprecated version of MockitoJUnitRunner, it might cause issues. Make sure to use the correct import statement for the MockitoJUnitRunner class1.

Misconfigured Test Setup: Verify that your test setup is correctly configured. This includes properly initializing mocks and ensuring that all necessary annotations are used correctly.

Classpath Issues: Check your classpath for any missing or conflicting dependencies that might cause the error.

Abstract Methods: Ensure that there are no abstract methods in the classes being mocked unless they are properly implemented.