Lucas Cummins reminded me of this site and said "More people need to know about this". I absolutely agree:
Formulon.io
It is a great tool created by Leif Gensert to test your new #Salesforce Formulas.
Instead of writing formulas and testing it on several records in your org, you can type the formula on this page and see the result right away.
Leif reimplemented most formula functions in #Javascript.
