How to Resolve Mockito Exception: Checked Exception is Invalid for This Method?

What does the Mockito exception 'checked exception is invalid for this method' mean, and how can I resolve it?

@Test
public void testMethod() throws Exception {
    when(mockedObject.methodWithCheckedException()).thenThrow(new SomeCheckedException()); // This might lead to an error
}

The Mockito exception indicating that a checked exception is invalid for a method typically arises when trying to throw a checked exception from a mocked method that does not declare it. This occurs due to Java's checked exception handling rules.

public class MockTest {
    @Mock
    SomeService mockedService;

    @Test(expected = SomeCheckedException.class)
    public void testMethod() throws Exception {
        when(mockedService.methodThatShouldThrow()).thenThrow(new SomeCheckedException());
        mockedService.methodThatShouldThrow(); // This will throw the checked exception
    }
}

Causes

• The method being mocked does not declare the checked exception in its signature.
• Mismatched exceptions between the mock setup and the actual method being called.

Solutions

• Ensure that the method being mocked properly declares the checked exception in its throws clause.
• Use a runtime exception instead if appropriate, as Mockito does not require runtime exceptions to be declared.

Mistake: Not declaring the checked exceptions in the method signature of the interface or class being mocked.

Solution: Always check the method signature in the original class or interface to ensure the exceptions are accounted for.

Mistake: Using a checked exception where a runtime exception is more appropriate.

Solution: Consider using a runtime exception to avoid this issue when mocking methods.