This part of code runs coverage,
cp.exec(cd ${rootProjectPath} && flutter test --coverage, (err, out) => {
When e.g. sources are located on disk d: on windows and VSCode is on disk c: then flutter test --coverage is not able to find test folder.
For test purpouses I changed it to:
cp.exec(d: && cd ${rootProjectPath} && flutter test --coverage, (err, out) => {
and it works.