Avoid repeating common parts of ProgramResults.

dart/tests/try/poi/source_update_test.dart

+// Copyright (c) 2014, 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.
+
+/// Test [source_update.dart].
+library trydart.source_update_test;
+
+import 'package:expect/expect.dart' show
+    Expect;
+
+import 'source_update.dart' show
+    expandUpdates;
+
+main() {
+  Expect.listEquals(
+      ["head v1 tail", "head v2 tail"],
+      expandUpdates(["head ", ["v1", "v2"], " tail"]));
+
+  Expect.listEquals(
+      ["head v1 tail v2", "head v2 tail v1"],
+      expandUpdates(["head ", ["v1", "v2"], " tail ", ["v2", "v1"]]));
+
+  Expect.throws(() {
+    expandUpdates(["head ", ["v1", "v2"], " tail ", ["v1"]]);
+  });
+
+  Expect.throws(() {
+    expandUpdates(["head ", ["v1", "v2"], " tail ", ["v1", "v2", "v3"]]);
+  });
+}