mockito/mockito · error · MockitoException

Only void methods can doNothing()! Example of correct use of

Error message

Only void methods can doNothing()!
Example of correct use of doNothing():
    doNothing().
    doThrow(new RuntimeException())
    .when(mock).someVoidMethod();
Above means:
someVoidMethod() does nothing the 1st time but throws an exception the 2nd time is called

What it means

Error "Only void methods can doNothing()! Example of correct use of doNothing(): doNothing(). doThrow(new RuntimeException()) .when(mock).someVoidMethod(); Above means: someVoidMethod() does nothing the 1st time but throws an exception the 2nd time is called" thrown in mockito/mockito.

Source

Thrown at mockito-core/src/main/java/org/mockito/internal/stubbing/answers/DoesNothing.java:35

    private static final long serialVersionUID = 4840880517740698416L;

    private static final DoesNothing SINGLETON = new DoesNothing();

    private DoesNothing() {}

    public static DoesNothing doesNothing() {
        return SINGLETON;
    }

    @Override
    public Object answer(InvocationOnMock invocation) {
        return null;
    }

    @Override
    public void validateFor(InvocationOnMock invocation) {
        if (!new InvocationInfo(invocation).isVoid()) {
            throw onlyVoidMethodsCanBeSetToDoNothing();
        }
    }
}

View on GitHub (pinned to 5a676bcd9e)

Solutions

1. Apply doNothing() only to void methods: doNothing().when(mock).someVoidMethod()
2. For non-void methods, use doReturn(value).when(mock).method() instead
3. Check for overloaded methods to ensure you are stubbing the intended signature

When it happens

Trigger: Thrown at mockito-core/src/main/java/org/mockito/internal/stubbing/answers/DoesNothing.java:35 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mockito/mockito@5a676bcd9e (2026-09-05). Data as JSON: /api/errors/eaba0f6972edb123. Report an issue: GitHub.