Refactor version_solver_test.

lib/src/sdk.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.
 
 /// Operations relative to the user's installed Dart SDK.
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:pub_semver/pub_semver.dart';
 
@@ skipping 11 matching lines @@
   // "/path/to/sdk".
   var aboveExecutable = p.dirname(p.dirname(Platform.resolvedExecutable));
   assert(fileExists(p.join(aboveExecutable, 'version')));
   return aboveExecutable;
 })();
 
 /// The SDK's revision number formatted to be a semantic version.
 ///
 /// This can be set so that the version solver tests can artificially select
 /// different SDK versions.
-Version version = _getVersion();
+final version = _getVersion();
 
 /// Determine the SDK's version number.
 Version _getVersion() {
   // Some of the pub integration tests require an SDK version number, but the
   // tests on the bots are not run from a built SDK so this lets us avoid
   // parsing the missing version file.
   var sdkVersion = Platform.environment["_PUB_TEST_SDK_VERSION"];
   if (sdkVersion != null) return new Version.parse(sdkVersion);
 
   if (!runningFromDartRepo) {
@@ skipping 22 matching lines @@
   var version = "$major.$minor.$patch";
   if (channel == "be") {
     // TODO(rnystrom): tools/utils.py includes the svn commit here. Should we?
     version += "-edge";
   } else if (channel == "dev") {
     version += "-dev.$prerelease.$prereleasePatch";
   }
 
   return new Version.parse(version);
 }