response = mock(CommonServerMessageBlock.class);
        }

        @Test
        @DisplayName("Should sign data correctly with zero signature field")
        void testSignZeroesSignatureField() {
            // Fill signature field with non-zero values
            for (int i = 0; i < SIGNATURE_LENGTH; i++) {
                data[SIGNATURE_OFFSET + i] = (byte) 0xFF;
            }