anchor.diff:            f.uri.toString().contains("/packages/")) &&
         f.uri.toString().endsWith("/.packages")));
   
  +  List<String> allCompilationErrors = [];
     for (File dotPackage in dotPackagesFiles) {
       Directory tempDir;
       Directory systemTempDir = Directory.systemTemp;
  
positive.code:   List<File> testFiles = new List<File>.from(testDir
        .listSync(recursive: true)
        .where((f) => f.path.endsWith("_test.dart") && !shouldSkip(f)));
    if (testFiles.isEmpty) return;
  
    Stopwatch stopwatch = new Stopwatch()..start();
  
  
negative.code:       Directory testDir =
            new Directory.fromUri(dotPackage.parent.uri.resolve("test/"));
        if (!testDir.existsSync()) continue;
        if (testDir.toString().contains("packages/flutter_web_plugins/test/")) {
          // TODO(jensj): Figure out which tests are web-tests, and compile those
          // in a setup that can handle that.
          continue;
        }
        print("Go for $testDir");
        List<String> compilationErrors = await attemptStuff(
            tempDir, flutterPlatformDirectory, dotPackage, testDir);
        if (compilationErrors.isNotEmpty) {
          print("Notice that we had ${compilationErrors.length} "
              "compilation errors for $testDir");
          allCompilationErrors.addAll(compilationErrors);
        }
      } finally {
        tempDir.delete(recursive: true);
      }
    }
    if (allCompilationErrors.isNotEmpty) {
      print("Had a total of ${allCompilationErrors.length} compilation errors:");
      allCompilationErrors.forEach(print);
      throw "Had a total of ${allCompilationErrors.length} compilation errors";
    }
  }
  
  Future<List<String>> attemptStuff(
      Directory tempDir,
      Directory flutterPlatformDirectory,
      File dotPackage,
      Directory testDir) async {
    File dillFile = new File('${tempDir.path}/dill.dill');
    if (dillFile.existsSync()) {
      throw "$dillFile already exists.";
  