Capybara::ChromeDevTools

Integrates chrome_remote (a Chrome DevTools Protocol client) with Capybara, letting you access Chrome DevTools via driver.dev_tools.

• Finds a free port and sets Chrome's --remote-debugging-port to this known port
• Starts crmux so that you can make additional connections to the Chrome DevTools/debugging port even while chromedriver continues to connect to the --remote-debugging-port (Chrome normally only allows one debugging session to be connected to a tab)
• Lets you inspect the browser window your tests are running in — even if they are running in a headless Chrome browser!
• Exposes a dev_tools method that provides access to a ChromeRemote instance (see capybara-chrome_response_headers, for one possible use for that)

Inspired by: https://stackoverflow.com/a/50876153/47185

Install crmux by running, for example:

npm install crmux -g

or

yarn add crmux

Test that you can run it with:

npx crmux --help

Add this line to your application's Gemfile:

gem 'capybara-chrome_dev_tools'

Enable this extension like so:

Capybara::ChromeDevTools.enabled = true

... before you do any action with Capybara that triggers it to use the Chrome driver/browser.

Add some code to your test to make it pause at the point where you want to inspect the state of the browser window. Otherwise, when the test finishes, it will close the window that you are inspecting and disconnect the DevTools frontend that you were using to view it.

Look for the output which teels you which port it's listening to:

Started crmux [pid 56630], listening at http://localhost:35720, connected to localhost:35719

Now you can go to http://localhost:35720, choose which window to inspect, and inspect the Chrome window that your tests are running in — all from this other Chrome browser instance!

You can also get the listen port from driver.crmux_listen_port if you want to automate things.

Access a ChromeRemote instance with dev_tools.

See chrome_remote for API documentation.

Example:

dev_tools.send_cmd "Page.enable"

This project should be considered a proof of concept.

It generally works, but isn't exceptionally resilient or stable.

Sometimes you may get intermittent errors from chrome_remote or the WebSocket connection. There should probably be some handling of these errors (or better yet, figure out what's causing the errors).

To get access to HTTP response status code, response headers, etc. from your tests, check out https://github.com/TylerRick/capybara-chrome_response_headers, which uses this gem.

Bug reports and pull requests are welcome on GitHub at https://github.com/TylerRick/capybara-chrome_dev_tools.