JavaScript Sentry: How to check if errors will be reported

One really simple way to check whether JavaScript Sentry integration was successful (raven-js or @sentry/browser), is to create an erroneous event handler like this:

<h1 onClick="throw new Error('JavaScript Sentry was successfully integrated')">
  My Website
</h1>

… and clicking on the element afterwards.

If your site has a strict CSP, see Using inline event handlers with a strict Content Security Policy (CSP).