IPLAYER-40770: Fix "No inspectable targets" error when connecting to chrome-remote-interface

[anthonyec]

Problem

Launching Chrome and connecting to the Chrome Dev Protocol (CDP) are separate actions, and are susceptible to a race condition. This race condition occurs if Chrome has launched but Chrome Dev Protocol is not yet ready.

If you try to connect to the Chrome Dev Protocol before it is ready, it will throw an error:

Error: No inspectable targets

We have been experiencing this in our iPlayer CI.

Solution

Wait for the Chrome Dev Protocol to be ready before trying to connect to it.

Chrome provides an endpoint (/json/list) that lists inspectable targets. If the CDP is not ready, the list will be an empty array. We can poll this endpoint until the list is populated. This is basically the solution that has been suggested in the bug report for the chrome-launcher library. However, there hasn't been an official fix merged yet.

Changes

• Install nock to mock requests
• Create simple GET request functionality (no need for third-party library)
• Add waitForInspectableTarget before trying to connect to CDP

Links

• Occasional "No inspectable targets" error when launching chrome with a very short connectionPollInterval GoogleChrome/chrome-launcher#145

[andymsuk]

Presumably everything still works as expected when running a11y-tests-web locally on your Mac too?

[anthonyec]

Presumably everything still works as expected when running a11y-tests-web locally on your Mac too?

@andymsuk yep, all works locally