Don't rely on directory traversal order in test.

test/command_line_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart_style.test.command_line;
 
 import 'dart:convert';
 
 import 'package:path/path.dart' as p;
 import 'package:scheduled_test/descriptor.dart' as d;
@@ skipping 108 matching lines @@
     });
   });
 
   group("--machine", () {
     test("writes each output as json", () {
       d.dir("code", [
         d.file("a.dart", unformattedSource),
         d.file("b.dart", unformattedSource)
       ]).create();
 
-      var process = runFormatterOnDir(["--machine"]);
-
-      var json = {
+      var jsonA = JSON.encode({
         "path": p.join("code", "a.dart"),
         "source": formattedSource,
         "selection": {"offset": -1, "length": -1}
-      };
+      });
 
-      process.stdout.expect(JSON.encode(json));
+      var jsonB = JSON.encode({
+        "path": p.join("code", "b.dart"),
+        "source": formattedSource,
+        "selection": {"offset": -1, "length": -1}
+      });
 
-      json["path"] = p.join("code", "b.dart");
-      process.stdout.expect(JSON.encode(json));
+      var process = runFormatterOnDir(["--machine"]);
 
+      // The order isn't specified.
+      process.stdout.expect(either(jsonA, jsonB));
+      process.stdout.expect(either(jsonA, jsonB));
       process.shouldExit();
     });
   });
 
   group("with no paths", () {
     test("errors on --overwrite.", () {
       var process = runFormatter(["--overwrite"]);
       process.shouldExit(64);
     });
 
     test("reads from stdin.", () {
       var process = runFormatter();
       process.writeLine(unformattedSource);
       process.closeStdin();
 
       // No trailing newline at the end.
       process.stdout.expect(formattedSource.trimRight());
       process.shouldExit();
     });
   });
 }