Add a JSON reporter.

lib/src/runner/version.dart

+// Copyright (c) 2015, 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:io';
+
+import 'package:yaml/yaml.dart';
+
+/// The version number of the test runner, or `null` if it couldn't be loaded.
+///
+/// This is a semantic version, optionally followed by a space and additional
+/// data about its source.
+final String testVersion = (() {
+  var lockfile;
+  try {
+    lockfile = loadYaml(new File("pubspec.lock").readAsStringSync());
+  } on FormatException catch (_) {
+    return null;
+  } on IOException catch (_) {
+    return null;
+  }
+
+  if (lockfile is! Map) return null;
+  var packages = lockfile["packages"];
+  if (packages is! Map) return null;
+  var package = packages["test"];
+  if (package is! Map) return null;
+
+  var source = package["source"];
+  if (source is! String) return null;
+
+  switch (source) {
+    case "hosted":
+      var version = package["version"];
+      if (version is! String) return null;
+
+      return version;
+
+    case "git":
+      var version = package["version"];
+      if (version is! String) return null;
+      var description = package["description"];
+      if (description is! Map) return null;
+      var ref = description["resolved-ref"];
+      if (ref is! String) return null;
+
+      return "$version (${ref.substring(0, 7)})";
+
+    case "path":
+      var version = package["version"];
+      if (version is! String) return null;
+      var description = package["description"];
+      if (description is! Map) return null;
+      var path = description["path"];
+      if (path is! String) return null;
+
+      return "$version (from $path)";
+
+    default: return null;
+  }
+})();