First pass at version constraint solver.

utils/tests/pub/pubspec_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('pubspec_test');
 
 #import('../../../lib/unittest/unittest.dart');
 #import('../../pub/pubspec.dart');
 #import('../../pub/source.dart');
 #import('../../pub/source_registry.dart');
 #import('../../pub/utils.dart');
+#import('../../pub/version.dart');
 
 class MockSource extends Source {
   final String name = "mock";
   final bool shouldCache = false;
   void validateDescription(description) {
     if (description != 'ok') throw new FormatException('Bad');
   }
 }
 
 main() {
   group('Pubspec', () {
     group('parse()', () {
+      test("allows a version constraint for dependencies", () {
+        var sources = new SourceRegistry();
+        sources.register(new MockSource());
+
+        var pubspec = new Pubspec.parse('''
+dependencies:
+  foo:
+    mock: ok
+    version: ">=1.2.3 <3.4.5"
+''', sources);
+
+        var foo = pubspec.dependencies[0];
+        expect(foo.name, equals('foo'));
+        expect(foo.constraint.allows(new Version(1, 2, 3)));
+        expect(foo.constraint.allows(new Version(1, 2, 5)));
+        expect(!foo.constraint.allows(new Version(3, 4, 5)));
+      });
+
       test("throws if the description isn't valid", () {
         var sources = new SourceRegistry();
         sources.register(new MockSource());
 
         throwsBadFormat(() {
         new Pubspec.parse('''
 dependencies:
   foo:
     mock: bad
 ''', sources);
         });
       });
     });
   });
 }
 
 throwsBadFormat(function) {
   expectThrow(function, (e) => e is FormatException);
 }