Add unit tests for X509 certificate date parsing
diff --git a/tests/suites/test_suite_x509parse.function b/tests/suites/test_suite_x509parse.function
index a724cd8..89f4609 100644
--- a/tests/suites/test_suite_x509parse.function
+++ b/tests/suites/test_suite_x509parse.function
@@ -613,16 +613,14 @@
                     int hour, int min, int sec )
 {
     mbedtls_x509_time time;
-    unsigned char buf[17];
+    unsigned char buf[21];
     unsigned char* start = buf;
     unsigned char* end = buf;
 
     memset( &time, 0x00, sizeof( time ) );
     *end = (unsigned char)tag; end++;
-    if( tag == MBEDTLS_ASN1_UTC_TIME )
-        *end = 13;
-    else
-        *end = 15;
+    *end = strlen( time_str );
+    TEST_ASSERT( *end < 20 );
     end++;
     memcpy( end, time_str, (size_t)*(end - 1) );
     end += *(end - 1);