Scope testem assets with a prefix

[stepankuzmin]

Testem uses an express serve-static middleware to serve the assets. It's mounted on the app root, meaning every request is first processed with the express.static middleware and only after that with the middlewares defined in the config, e.g., proxy middleware.

This ends up in a bunch of extra fs.stat calls which bloat the server response time. You can check that by enabling the DEBUG=send environment variable and making a request to the server.

const testemConfig = {
    middleware: [
        (app) => app.use('/render-tests', serveStatic(path.join(__dirname, 'render-tests')))
    ]
};

Considering the configuration above, all requests with the /render-tests prefix are used for lookup files in the testem/public/ folder first, which should be avoided.

send stat "/mnt/ramdisk/mapbox-gl-js/node_modules/testem/public/render-tests/background-color/default/expected.png" +90ms
send stat "/mnt/ramdisk/mapbox-gl-js/test/integration/render-tests/background-color/default/expected.png" +1ms
send pipe "/mnt/ramdisk/mapbox-gl-js/test/integration/render-tests/background-color/default/expected.png" +0ms

This PR scopes all requests to the /testem prefix to the testem's /public/testem dir, which fixes that issue.

[stepankuzmin]

I see some integration tests are failing with GPU process isn't usable, but I'm unable to reproduce it locally with npm run integration. Probably some CI configuration issue?

[johanneswuerbach]

Could you rebase your PR? CI should be fixed in the latest main :-)

[stepankuzmin]

Hey @johanneswuerbach,
Sure, thanks for the fix!

[johanneswuerbach]

Published as testem@3.10.1. Thank you 🤩

[stepankuzmin]

Awesome, thanks! 🙏