There are few useful tools could be use to test some parameter before you start configure SSO connection with the IdP provider:
If you want to test SP initiate SSO and your IdP is Microsoft Online (https://login.microsoftonline.com), you can to the following
https://idp.ssocircle.com/sso/toolbox/samlEncode.jsp
Therre is another useful tool set avaiable here : https://www.samltool.com/url.php
It provides many useful tools: