Fix name conflict and implicit use of functions from string.h
diff --git a/tests/suites/test_suite_debug.function b/tests/suites/test_suite_debug.function
index 98f98b0..a32eba0 100644
--- a/tests/suites/test_suite_debug.function
+++ b/tests/suites/test_suite_debug.function
@@ -1,5 +1,6 @@
 /* BEGIN_HEADER */
 #include "mbedtls/debug.h"
+#include "string.h"
 
 struct buffer_data
 {