}
    }

    @Nested
    @DisplayName("Combine Tests")
    class CombineTests {

        @Test
        @DisplayName("Should combine two referral data objects")
        void testCombine() {
            // Setup first referral
            DfsReferralDataImpl first = new DfsReferralDataImpl();
            when(mockReferral.getTtl()).thenReturn(300);
            when(mockReferral.getRFlags()).thenReturn(0);

            boolean result = concreteImplementation.isIntermediate();
            assertNotNull(result);
        }

        @Test
        @DisplayName("Should combine referral data")
        void testCombine() {
            DfsReferralDataInternal combined = mock(DfsReferralDataInternal.class);

            // Test with mock
            when(mockReferralData.combine(mockDfsReferralData)).thenReturn(combined);