[test]: Add tests for utils to find project root

[anshumanv]

Do you want to request a feature or report a bug?
I think we should have tests for util to find project root present in path-utils - https://github.com/webpack/webpack-cli/blob/master/packages/utils/path-utils.ts

What is the current behavior?
No tests for the function

If the current behavior is a bug, please provide the steps to reproduce.
NA

What is the expected behavior?
Have some tests to test behavior in various cases.

If this is a feature request, what is motivation or use case for changing the behavior?
NA

Please paste the results of webpack-cli info here, and mention other relevant information such as programming language.

  System:
    OS: macOS 10.14.5
    CPU: (4) x64 Intel(R) Core(TM) i5-5250U CPU @ 1.60GHz
  Binaries:
    Node: 10.15.3 - /usr/local/bin/node
    Yarn: 1.12.3 - /usr/local/bin/yarn
    npm: 6.4.1 - /usr/local/bin/npm
  Browsers:
    Chrome: 75.0.3770.100
    Safari: 12.1.1
  npmPackages:
    webpack: 4.x.x => 4.33.0
    webpack-dev-server: 3.7.1 => 3.5.1
  npmGlobalPackages:
    webpack-cli: 3.3.4
    webpack: 4.30.0

[anshumanv]

@evenstensberg @ematipico is it within scope to add tests for this?

[ematipico]

The only way that I can come up with a way of testing such things is by using Docker. Are you aware of a better way to test them?

[evenstensberg]

I think we've had some PR's to fix this, @anshumanv ?

[anshumanv]

Maybe other utils but not the findProjectRoot function.

[evenstensberg]

Could you send a pr?