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adrienpoly/application.html.erb

Last active November 3, 2024 13:14
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Capybara / Stimulus test helper to ensure JS is ready when test starts
Raw
application.html.erb
<!DOCTYPE html>
<html>
<head>
...
</head>
<body data-controller="js">
<%= yield %>
</body>
</html>
Raw
js_controller.js
import { Controller } from 'stimulus'
export default class extends Controller {
static values = { loaded: Boolean }
connect() {
this.loadedValue = true
}
}
Raw
some_system_test_spec.rb
# ...
scenario 'test some js behavior', js: true do
visit some_path
ensure_js_is_ready
# JS is fully loaded you can start interacting with the page
end
# ...
Raw
system_spec_helpers.rb
def ensure_js_is_ready
expect(page).to have_css('[data-js-loaded-value="true"]')
end
@andrewyoo
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I've been playing around with this as well. I noticed when i load all my controllers using import "controllers", they appear to load alphabetically when i put console.log in the various connect() function. So i renamed the js_controller to zz_js_controller and i'm going to try that out.

Given it's an intermittent issue only in my system tests, i can't confirm if it will fix anything. Thanks for this post though!

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ghost commented Feb 7, 2024

@andrewyoo Did it work?

@andrewyoo
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@alan-pie Yes, it works very well. I have no intermittent issues after implementing it in my CI tests and identifying the problem areas (right after a visit).

@rogerkk
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rogerkk commented Nov 3, 2024 •
edited
Loading

Thanks for this idea!

We're lazy loading Stimulus controllers and this didn't fully solve our flaky tests. Since lazy loading controllers get loaded in the order in which they occur in the DOM, this solution seems to work best when referencing the controller at the very end of the document. Something like this:

<!DOCTYPE html>
<html>
  <head>
    ...
  </head>

  <body>
    <%= yield %>
  </body>
  
  <js-testing data-controller="js" />
</html>

I know this kind of self-closing is invalid HTML, but for some reason the tag needs to be self closing for the controller to be executed. Haven't had the time to dig into that.

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