diff --git a/lib/common/tests/io/pcmk__full_path_test.c b/lib/common/tests/io/pcmk__full_path_test.c
index c3092b15bf..7c8bddade6 100644
--- a/lib/common/tests/io/pcmk__full_path_test.c
+++ b/lib/common/tests/io/pcmk__full_path_test.c
@@ -1,41 +1,55 @@
 /*
- * Copyright 2020-2021 the Pacemaker project contributors
+ * Copyright 2020-2022 the Pacemaker project contributors
  *
  * The version control history for this file may have further details.
  *
  * This source code is licensed under the GNU Lesser General Public License
  * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
  */
 
 #include <crm_internal.h>
 
 #include <crm/common/unittest_internal.h>
 
+#include "mock_private.h"
+
+static void
+function_asserts(void **state)
+{
+    pcmk__assert_asserts(pcmk__full_path(NULL, "/dir"));
+    pcmk__assert_asserts(pcmk__full_path("file", NULL));
+
+    pcmk__mock_strdup = true;       // strdup() will return NULL
+    pcmk__assert_asserts(pcmk__full_path("/full/path", "/dir"));
+    pcmk__mock_strdup = false;      // Use real strdup()
+}
+
 static void
 full_path(void **state)
 {
     char *path = NULL;
 
     path = pcmk__full_path("file", "/dir");
     assert_int_equal(strcmp(path, "/dir/file"), 0);
     free(path);
 
     path = pcmk__full_path("/full/path", "/dir");
     assert_int_equal(strcmp(path, "/full/path"), 0);
     free(path);
 
     path = pcmk__full_path("../relative/path", "/dir");
     assert_int_equal(strcmp(path, "/dir/../relative/path"), 0);
     free(path);
 }
 
 int
 main(int argc, char **argv)
 {
     const struct CMUnitTest tests[] = {
+        cmocka_unit_test(function_asserts),
         cmocka_unit_test(full_path),
     };
 
     cmocka_set_message_output(CM_OUTPUT_TAP);
     return cmocka_run_group_tests(tests, NULL, NULL);
 }