diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 965d520..c9269d5 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -794,9 +794,21 @@
     make TEST_CPP=1
 }
 
+component_test_check_params_functionality () {
+    msg "build+test: MBEDTLS_CHECK_PARAMS functionality"
+    scripts/config.pl full # includes CHECK_PARAMS
+    # Make MBEDTLS_PARAM_FAILED call mbedtls_param_failed().
+    scripts/config.pl unset MBEDTLS_CHECK_PARAMS_ASSERT
+    scripts/config.pl unset MBEDTLS_MEMORY_BUFFER_ALLOC_C
+    # Only build and run tests. Do not build sample programs, because
+    # they don't have a mbedtls_param_failed() function.
+    make CC=gcc CFLAGS='-Werror -O1' lib test
+}
+
 component_test_check_params_without_platform () {
     msg "build+test: MBEDTLS_CHECK_PARAMS without MBEDTLS_PLATFORM_C"
     scripts/config.pl full # includes CHECK_PARAMS
+    # Keep MBEDTLS_PARAM_FAILED as assert.
     scripts/config.pl unset MBEDTLS_MEMORY_BACKTRACE # too slow for tests
     scripts/config.pl unset MBEDTLS_MEMORY_BUFFER_ALLOC_C
     scripts/config.pl unset MBEDTLS_PLATFORM_EXIT_ALT
@@ -814,6 +826,7 @@
     msg "build+test: MBEDTLS_CHECK_PARAMS with alternative MBEDTLS_PARAM_FAILED()"
     scripts/config.pl full # includes CHECK_PARAMS
     scripts/config.pl unset MBEDTLS_MEMORY_BACKTRACE # too slow for tests
+    # Set MBEDTLS_PARAM_FAILED to nothing.
     sed -i 's/.*\(#define MBEDTLS_PARAM_FAILED( cond )\).*/\1/' "$CONFIG_H"
     make CC=gcc CFLAGS='-Werror -O1' all test
 }