anchor.diff:        await d.file("other.scss", "a {b: c}").create();
         await d.file("test.scss", "@import 'other'").create();
   
  -      var sass =
  -          await runSass(["--no-source-map", "--update", "test.scss:out.css"]);
  +      var sass = await update(["test.scss:out.css"]);
         expect(sass.stdout, emits('Compiled test.scss to out.css.'));
         await sass.shouldExit(0);
   
         await tick;
         await d.file("other.scss", "x {y: z}").create();
   
  -      sass =
  -          await runSass(["--no-source-map", "--update", "test.scss:out.css"]);
  +      sass = await update(["test.scss:out.css"]);
         expect(sass.stdout, emits('Compiled test.scss to out.css.'));
         await sass.shouldExit(0);
   
  
positive.code: 
  /// Defines test that are shared between the Dart and Node.js CLI test suites.
  void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
    group("updates CSS", () {
      test("that doesn't exist yet", () async {
        await d.file("test.scss", "a {b: c}").create();
  
        var sass =
            await runSass(["--no-source-map", "--update", "test.scss:out.css"]);
        expect(sass.stdout, emits('Compiled test.scss to out.css.'));
        await sass.shouldExit(0);
  
  
negative.code:     });
  
      test("from stdin", () async {
        var sass = await update(["-:out.css"]);
        sass.stdin.writeln("a {b: c}");
        sass.stdin.close();
        expect(sass.stdout, emits('Compiled stdin to out.css.'));
  