Add a tip to test ssl certs.

Debugging-Https-bugs-using-Charles.md

@@ -27,6 +27,16 @@ which will do the installation for you.
 
 # Development details
 
+### Testing SSL issues
+
+In some cases you might be getting exceptions from CFNetwork regarding the SSL certificates of certain url. There is no need for you to write your own application, you can use nscurl to use the CFNetwork Apple API to test the SSL certificates and other features as background sessions:
+
+The following command is an example on how to test the ssl certs of a known url:
+
+`nscurl --ats-diagnostics https://microsoft.com`
+
+Which will print which versions fail.
+
 ### HttpClient
 
 There are several implementations of the HttpClient, each of them might need to be set to use the system proxy in order to be able to sniff the communication.