pkg/mime: Use pkg/test

test/mime_type_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.
 
 import 'dart:math' as math;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:mime/mime.dart';
 import 'package:mime/src/magic_number.dart';
 
 void _expectMimeType(String path,
                     String expectedMimeType,
                     {List<int> headerBytes,
                      MimeTypeResolver resolver}) {
   String mimeType;
   if (resolver == null) {
     mimeType = lookupMimeType(path, headerBytes: headerBytes);
@@ skipping 84 matching lines @@
   });
 
   test('default magic number', () {
     var actualMaxBytes = DEFAULT_MAGIC_NUMBERS.fold(0, (previous, magic) {
       return math.max(previous, magic.numbers.length);
     });
 
     expect(defaultMagicNumbersMaxLength, actualMaxBytes);
   });
 }