Hello @eroetman

Sorry for the delays, it's been a crazy week.

First of all, thanks for taking the time to fix this issue.
I've finally taken the time to further investigate the issue, and it looks like the optional compilerOptions parameter became mandatory, while the enum that references the names of the compiler still only contains "typescript".

This means that we can't provide

this.externalCompilers = [
  new TestcafeESNextCompiler(compilerOptions[CustomizableCompilers.esnext]),
  new TestcafeTypescriptCompiler(compilerOptions[CustomizableCompilers.typescript]),
];

because CustomizableCompilers.esnext doesn't exist.

However, providing CustomizableCompilers.typescript instead makes very little sense, because we are not working with typescript here.

We can't decide to not provide anything (as the parameter is now expected to be defined, which is what causes the issue in the first place)

For minimal impact on the code, I'd rather give the function an empty obect:

this.externalCompilers = [
  new TestcafeESNextCompiler({}),
  new TestcafeTypescriptCompiler(compilerOptions[CustomizableCompilers.typescript]),
];

This means that we keep using whatever TestCafe considers the default values of any option that could be passed down. Basically, nothing changed compared to the original code, which has been running long enough that I'm confident it works.

I'll add remarks on other parts of the code, but nothing major, just me nitpicking :)

My first adventure on GitHub.... It took some time because my main computer won't work as well with github as with my company source control system, will try to solve that coming week.
Thank you for taking the time to dive into this issue. I look forward to using gherkin with Testcafe 1.20 because then we can start using testcafé's API-testing possibility and maybe replace Supertest with this.