Running single tests does not work

[tsmaeder]

Bug Description:

I can't run single tests from the theia/examples/playwright project on Windows. I always end up with "zero tests found"

Steps to Reproduce:

1. Check out and build theia on Windows
2. Run the browser app as per playwright documetation
3. open a cmd instance on theia/examples/playwright
4. Type yarn ui-tests-headful .\src\tests\theia-app.test.ts
5. Observe: the system complains it can't find any tests:

Running 0 test using 0 worker


=================
 no tests found.
=================

error Command failed with exit code 1.

The complete test suite starts correctly if I omit the file parameter. I am following the guide in "examples\playwright\GETTING-STARTED.md" and would expect the test in the designated file to be executed.

Additional Information

I tried to do the following, but with the same result:

• Different test files
• Using the compiled files in lib instead of the *.ts-files in src
• Using forward slashes instead of backslashes