Test that xxx_free() functions accept NULL parameter
diff --git a/tests/suites/test_suite_chachapoly.function b/tests/suites/test_suite_chachapoly.function
index 51cc0ab..8e56bf6 100644
--- a/tests/suites/test_suite_chachapoly.function
+++ b/tests/suites/test_suite_chachapoly.function
@@ -139,6 +139,7 @@
     memset( mac,    0x00, sizeof( mac ) );
 
     TEST_INVALID_PARAM( mbedtls_chachapoly_init( NULL ) );
+    TEST_VALID_PARAM( mbedtls_chachapoly_free( NULL ) );
 
     /* setkey */
     TEST_INVALID_PARAM_RET( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA,