diff --git a/tests/suites/test_suite_dhm.data b/tests/suites/test_suite_dhm.data
index fcfc5cf..005784d 100644
--- a/tests/suites/test_suite_dhm.data
+++ b/tests/suites/test_suite_dhm.data
@@ -10,6 +10,8 @@
 Diffie-Hellman full exchange: 5-bit, x_size=2
 dhm_do_dhm:10:"23":2:10:"5":0
 
+## Repeat this test case and a few similar ones several times. The RNG state
+## changes, so we get to exercise the code with a few different values.
 Diffie-Hellman full exchange: 5-bit #1
 dhm_do_dhm:10:"23":1:10:"5":0
 
diff --git a/tests/suites/test_suite_dhm.function b/tests/suites/test_suite_dhm.function
index 43dcd56..2e8644d 100644
--- a/tests/suites/test_suite_dhm.function
+++ b/tests/suites/test_suite_dhm.function
@@ -1,6 +1,9 @@
 /* BEGIN_HEADER */
 #include "mbedtls/dhm.h"
 
+/* Sanity checks on a Diffie-Hellman parameter: check the length-value
+ * syntax and check that the value is the expected one (taken from the
+ * DHM context by the caller). */
 static int check_dhm_param_output( const mbedtls_mpi *expected,
                                    const unsigned char *buffer,
                                    size_t size,
@@ -28,6 +31,8 @@
     return( ok );
 }
 
+/* Sanity checks on Diffie-Hellman parameters: syntax, range, and comparison
+ * against the context. */
 static int check_dhm_params( const mbedtls_dhm_context *ctx,
                              size_t x_size,
                              const unsigned char *ske, size_t ske_len )