testAnalyzeAndRun method
Analyze a Dart file and runs this assist in test mode.
The result will contain all the changes that would have been applied by run.
Implementation
@visibleForTesting
Future<List<AnalysisError>> testAnalyzeAndRun(File file) async {
  final result = await resolveFile2(path: file.path);
  result as ResolvedUnitResult;
  return testRun(result);
}