(split) Add unit tests for TLSSocket and TLSSocketWrapper

This also includes their Datagram counterparts: DTLSSocket and DTLSSocketWrapper.
Coverage missing for timer-related functionality, but this would require more advanced stub development.
The extra (d)tls_test_config.h is necessary for successful compilation without HW support for the mbedtls features in unittests.
I reused the mbedtls stub found in features/nanostack/coap-service/test/coap-service/unittest/stub/mbedtls_stub.c and amended it slightly with a few missing functions.

Author: michalpasztamobica

test/coap-service/unittest/stub/mbedtls_stub.c

@@ -59,7 +59,12 @@ void mbedtls_ssl_conf_max_version(mbedtls_ssl_config *conf, int major, int minor
 
 }
 
-void mbedtls_ssl_config_init(mbedtls_ssl_config *a)
+void mbedtls_ssl_conf_transport( mbedtls_ssl_config *conf, int transport )
+{
+
+}
+
+void mbedtls_ssl_config_init( mbedtls_ssl_config *a )
 {
 
 }
@@ -198,6 +203,16 @@ int mbedtls_ssl_write(mbedtls_ssl_context *a, const unsigned char *b, size_t c)
     return mbedtls_stub.expected_int;
 }
 
+int mbedtls_ssl_set_hostname( mbedtls_ssl_context *ssl, const char *hostname )
+{
+    return 0;
+}
+
+const mbedtls_x509_crt *mbedtls_ssl_get_peer_cert( const mbedtls_ssl_context *ssl )
+{
+    return NULL;
+}
+
 
 
 //From crt_drbg.h
@@ -252,6 +267,18 @@ int mbedtls_x509_crt_parse(mbedtls_x509_crt *a, const unsigned char *b, size_t c
     return mbedtls_stub.expected_int;
 }
 
+int mbedtls_x509_crt_info( char *buf, size_t size, const char *prefix,
+                   const mbedtls_x509_crt *crt )
+{
+    return 0;
+}
+
+int mbedtls_x509_crt_verify_info( char *buf, size_t size, const char *prefix,
+                          uint32_t flags )
+{
+    return 0;
+}
+
 //From entropy.h
 void mbedtls_entropy_init(mbedtls_entropy_context *a)
 {
@@ -356,3 +383,6 @@ int mbedtls_ssl_session_reset(mbedtls_ssl_context *ssl)
     }
     return mbedtls_stub.expected_int;
 }
+
+void mbedtls_strerror( int ret, char *buf, size_t buflen ){
+}