Confusing and not very useful
Ive used a few of these kind of apps (RegExhibit, RegExRX, etc) and this is probably the worst value for the money.
The whole app is a clunky UX nightmare. Its got a ton of features that are unclear how to use and provide little feed back. Even simple things like determining if a regex valid arent obvious. The color changes but is the bright color valid or invaid?
Whats the language selection supposed to do? It doesnt seem to matter what you pick so it comes off like a gimic… Is it copying to the clipboard? Syntax highlighting? Ive got no idea and theres no feedback.
The tests bit could be useful as a way to track test cases but they dont take the step of letting you see the effect of changes wihtout selecting each one.
graveltech about Oyster - Your Regex IDE