Validate common mark flavors in tests

pkgs/markdown/test/common_mark_test.dart

diff --git a/pkgs/markdown/test/common_mark_test.dart b/pkgs/markdown/test/common_mark_test.dart
new file mode 100644
index 0000000..f480037
--- /dev/null
+++ b/pkgs/markdown/test/common_mark_test.dart
@@ -0,0 +1,43 @@
+// Copyright (c) 2017, 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.
+
+import 'dart:convert';
+
+import 'package:test/test.dart';
+
+import '../tool/stats_lib.dart';
+
+void main() {
+  _registerTests(Config.commonMarkConfig);
+  _registerTests(Config.gfmConfig);
+}
+
+void _registerTests(Config config) {
+  var tests = loadCommonMarkSections(config.prefix);
+
+  var statsFile = getStatsFile(config.prefix);
+  var statsJson = JSON.decode(statsFile.readAsStringSync())
+      as Map<String, Map<String, String>>;
+
+  group(config.prefix, () {
+    tests.forEach((section, examples) {
+      group(section, () {
+        var sectionStats = statsJson[section];
+        for (var e in examples) {
+          test('Example ${e.example}', () {
+            var expected = sectionStats[e.example.toString()];
+
+            expect(expected, isNotNull);
+
+            var result = compareResult(config, e, throwOnError: true);
+
+            // not super-pretty way to get the value section of an enum
+            var resultString = result.toString().split('.')[1];
+            expect(resultString, expected);
+          });
+        }
+      });
+    });
+  });
+}