pkg/csslib: use pkg/test and allow latest version of logging pkg

test/mixin_test.dart

 // Copyright (c) 2013, 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 mixin_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
+
 import 'testing.dart';
 
 compileAndValidate(String input, String generated) {
   var errors = [];
   var stylesheet = compileCss(input, errors: errors, opts: options);
   expect(stylesheet != null, true);
   expect(errors.isEmpty, true, reason: errors.toString());
   expect(prettyPrint(stylesheet), generated);
 }
 
@@ skipping 631 matching lines @@
     test('multiple args and var decls as args', mixinManyArgs);
   });
 
   group('Mixin warnings', () {
     test('undefined top-level', undefinedTopLevel);
     test('undefined declaration', undefinedDeclaration);
     test('detect bad top-level as declaration', badDeclarationInclude);
     test('detect bad declaration as top-level', badTopInclude);
   });
 }