Migrate tests to using package test

test/int32_test.dart

 // Copyright (c) 2012, 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 Int32test;
 
 import 'package:fixnum/fixnum.dart';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 
 void main() {
   group("isX tests", () {
     test("isEven", () {
       expect((-Int32.ONE).isEven, false);
       expect(Int32.ZERO.isEven, true);
       expect(Int32.ONE.isEven, false);
       expect(Int32.TWO.isEven, true);
     });
     test("isMaxValue", () {
@@ skipping 399 matching lines @@
       expect(new Int32(-1).shiftRightUnsigned(8).toHexString(), "ffffff");
     });
   });
 
   group("toRadixString", () {
     test("returns base n string representation", () {
       expect(new Int32(123456789).toRadixString(5), "223101104124");
     });
   });
 }