verify(mockDigest).sign(eq(buffer), eq(0), anyInt(), eq(testMessage), isNull());
        }

        @Test
        @DisplayName("Should retain payload when requested")
        void testEncodeRetainPayload() {
            byte[] buffer = new byte[1024];
            testMessage.setBytesWritten(10);
            testMessage.retainPayload();

            int len = testMessage.encode(buffer, 0);