i3 is nice. End to end tests are nice. Chromium is nice. But they don't get along so well by default.
When you run you e2e script with nodemon, each run opens and closes the test browser window. By default, that window appears right by your editor, messing the layout.
It's easy to fix though : you just need to tell i3 what to do with that test browser window.
To make every new chromium window appear in the workspace $ws5, add this in ~/.config/i3/config
assign [class="Chromium-browser"] → $ws5
The workspace name is a variable here, but you can put anything. I assign that window to a rarely used workspace.
Chromium has a different class from Google Chrome, so this has no impact on where the "real" browser is started.
To get the class infos for other browsers, run
xprop in a terminal and then click on a window.