Whether or not a SSL certificate is required to connect with StoneEdge, really depends on their integration requirements. In other words, yes it may be valid that a SSL certificate is required.
A SSL certificate can certainly be created/acquired for testing purposes. However, you will have to determine what type of certificate will support your testing needs.
For example, when appropriate I may use a self-signed certificate. In other instances, I may need a certificate signed by a trusted CA. It may also be useful to note that some providers, like Comodo, offer free trial SSL certificates.