Add support for specifying SDK version constraints in pubspecs.

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 '../../../pkg/unittest/lib/unittest.dart';
+import 'test_pub.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, {bool fromLockFile: false}) {
@@ skipping 87 matching lines @@
       test("allows comment-only files", () {
         var pubspec = new Pubspec.parse('''
 # No external dependencies yet
 # Including for completeness
 # ...and hoping the spec expands to include details about author, version, etc
 # See http://www.dartlang.org/docs/pub-package-manager/ for details
 ''', sources);
         expect(pubspec.version, equals(Version.none));
         expect(pubspec.dependencies, isEmpty);
       });
+
+      group("environment", () {
+        test("defaults to any SDK constraint if environment is omitted", () {
+          var pubspec = new Pubspec.parse('', sources);
+          expect(pubspec.environment.sdkVersion, equals(VersionConstraint.any));
+        });
+
+        test("allows an empty environment map", () {
+          var pubspec = new Pubspec.parse('''
+environment:
+''', sources);
+          expect(pubspec.environment.sdkVersion, equals(VersionConstraint.any));
+        });
+
+        test("throws if the environment value isn't a map", () {
+          expectFormatError('''
+environment: []
+''');
+        });
+
+        test("allows a version constraint for the sdk", () {
+          var pubspec = new Pubspec.parse('''
+environment:
+  sdk: ">=1.2.3 <2.3.4"
+''', sources);
+          expect(pubspec.environment.sdkVersion,
+              equals(new VersionConstraint.parse(">=1.2.3 <2.3.4")));
+        });
+
+        test("throws if the sdk isn't a string", () {
+          expectFormatError('''
+environment:
+  sdk: []
+''');
+        });
+
+        test("throws if the sdk isn't a valid version constraint", () {
+          expectFormatError('''
+environment:
+  sdk: "oopies"
+''');
+        });
+      });
     });
   });
 }