anchor.diff:        file.writeAsStringSync("pkgA() {}");
   
         // Package B.
  -      file = File('${tempDir.path}/pkgB/.packages')
  -        ..createSync(recursive: true);
  -      file.writeAsStringSync("pkgA: ../pkgA");
         file = File('${tempDir.path}/pkgB/a.dart')..createSync(recursive: true);
         file.writeAsStringSync("pkgB_a() {}");
         file = File('${tempDir.path}/pkgB/b.dart')..createSync(recursive: true);
  
positive.code:           "pkgB_b() { pkgA(); }");
  
        // Application.
        file = File('${tempDir.path}/app/.packages')..createSync(recursive: true);
        file.writeAsStringSync("pkgA:../pkgA\n"
            "pkgB:../pkgB");
  
negative.code:         var main = File('${tempDir.path}/foo.dart')..createSync();
          main.writeAsStringSync(
              "import 'package:foo/foo.dart'; main() {print(foo);}\n");
          File('${tempDir.path}/.dart_tool/package_config.json')
            ..createSync(recursive: true)
            ..writeAsStringSync('''
    {
      "configVersion": 2,
      "packages": [
        {
          "name": "foo",
          "rootUri": "http://$host:$port/packages/foo",
          "packageUri": "./"
        }
      ]
    }
  ''');
          File('${tempDir.path}/packages/foo/foo.dart')
            ..createSync(recursive: true)
            ..writeAsStringSync("var foo = 'hello';");
  