Sometimes end-to-end tests talk to external processes and/or servers. Sometimes those external things take a little while to do their stuff. Sometimes you need to assert that stuff happens, eventually.
npm install patience
When you want to make sure something happens within a short time period, call
soon(assert, context, callback). This will repeatedly check the
assert until it passes, or gives up trying.
Here's something that hopefully gets the idea across. Say I have an assert that looks like this:
That's great if the users list is updated synchronously. But say I'm testing my code in a child process, and using socket.io to send users back to a zombie browser when they log in? The test will only pass if the assert happens to run after all that communication has finished.
Instead, I can give it a short while to happen:
This makes my test pass reliably, and as quickly as possible.
Or if I need to check that an async function eventually succeeds (i.e. calls the callback without passing it an error):