In terms to test the auth request and encode url, I would like to recommend a Chrome extension, Postman.
In Postman, parameters you enter in the URL bar or in the key/value editor will not automatically be URL-encoded. Right click on a piece of selected text, and click EncodeURIComponent
to manually encode the parameter value.

You can individually add key/value
pairs and Postman will combine everything together. If your URL already has parameters - for example, if you are pasting a URL from some other source, Postman will split the URL into pairs automatically.