4.0.0.beta - Skipped tests with coverage analysis can result in an error

[nicojs]

When running Stryker on "vscode-python" (thanks @gramster for this gem 💎), you can run into this error:

11:13:28 (1251) ERROR Stryker an error occurred InjectionError: Could not inject [class MutationTestExecutor] -> [token "mutantsWithTestCoverage"] -> [function findMutantTestCoverage]. Cause: Found test with id "Process - PythonExecutionFactory Without a resource Ensure create returns a CondaExecutionService instance if createCondaExecutionService() returns a valid object" in coverage data, but not in the test results of the dry run. This shouldn't happen! Please report the issue at the issue tracker of your stryker test runner

The message is self explanatory. There appears to be data missing in the dry run result.

The specified test looks like this:

test('Ensure `create` returns a CondaExecutionService instance if createCondaExecutionService() returns a valid object', async function () {
  // tslint:disable-next-line:no-invalid-this
  return this.skip();
  // [...]  
});

My conclusion is that we're not handling skipped tests correctly.