Support custom port for web-test-runner-plugin to avoid port conflicts between tests and dev server

[dwilson6]

It looks like there currently isn't a way to pass a custom port to the web-test-runner-plugin. If I have snowpack dev running in one terminal and then run the tests in another terminal, it will always pop up with the port conflict message ! Port 3000 not available. Run on port 3001 instead? (Y/n). It would be nice if I could 1) choose a custom port to use for the test run, 2) tell it to always try the next port without the prompt, or 3) use the existing server (which may not be the best option).

I was looking at the plugin code and it looks like there already is a mechanism for overriding snowpackConfig. Would it make sense to merge user provided overrides on top of the overrides in the plugin itself in the call to loadConfiguration? I am happy to submit a PR with that change or try a different approach.

[dwilson6]

Here's a first pass at allowing config overrides for the snowpack server instance used by the plugin. #2430

[LarsDenBakker]

The snowpack plugin should not need to open any port at all, since the test runner serves to the browser.

[dwilson6]

It runs its own server though. But Fred recommended a better solution of using NODE_ENV in the snowpack config.

[LarsDenBakker]

Right, but it shouldn't start a server because it's unused when used as a plugin inside the test runner.

[dwilson6]

Ah, I see what you mean now. Yeah I was a little surprised the plugin was starting its own server when I first saw that.