verifyNoMoreInteractions(locator);
    }

    // Invalid input: null reqPath leads to NPE from implementation
    @Test
    @DisplayName("handleDFSReferral throws NPE on null reqPath")
    void handleDfsReferralNullPathThrows() {
        when(locator.handleDFSReferral(any(), isNull())).thenThrow(new NullPointerException("reqPath"));