Use the new test runner.

test/version_range_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 pub_semver.test.version_range_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 
 import 'package:pub_semver/pub_semver.dart';
 
 import 'utils.dart';
 
 main() {
   group('constructor', () {
     test('takes a min and max', () {
       var range = new VersionRange(min: v123, max: v124);
       expect(range.isAny, isFalse);
@@ skipping 175 matching lines @@
       expect(new VersionRange(min: v123, max: v124).intersect(v114).isEmpty,
           isTrue);
     });
   });
 
   test('isEmpty', () {
     expect(new VersionRange().isEmpty, isFalse);
     expect(new VersionRange(min: v123, max: v124).isEmpty, isFalse);
   });
 }