Add a Loader class for loading tests from files.

lib/src/loader.dart

Index: lib/src/loader.dart
diff --git a/lib/src/loader.dart b/lib/src/loader.dart
new file mode 100644
index 0000000000000000000000000000000000000000..e5b843c503d38044ca725ecdcbf9226858a4fb0b
--- /dev/null
+++ b/lib/src/loader.dart
@@ -0,0 +1,95 @@
+// 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.
+
+library unittest.loader;
+
+import 'dart:async';
+import 'dart:io';
+import 'dart:isolate';
+
+import 'package:path/path.dart' as p;
+
+import 'dart.dart';
+import 'isolate_test.dart';
+import 'suite.dart';
+
+/// A class for finding test files and loading them into a runnable form.
+class Loader {
+  /// The package root to use for loading tests, or `null` to use the automatic
+  /// root.
+  final String _packageRoot;
+
+  /// All isolates that have been spun up by the loader.
+  final _isolates = new Set<Isolate>();
+
+  /// Creates a new loader.
+  ///
+  /// If [packageRoot] is passed, it's used as the package root for all loaded
+  /// tests. Otherwise, the `packages/` directories next to the test entrypoints
+  /// will be used.
+  Loader({String packageRoot})
+      : _packageRoot = packageRoot;
+
+  /// Loads all test suites in [dir].
+  ///
+  /// This will load tests from files that end in "_test.dart".
+  Future<Set<Suite>> loadDir(String dir) {
+    return Future.wait(new Directory(dir).listSync(recursive: true)
+        .map((entry) {
+      if (entry is! File) return new Future.value();
+      if (!entry.path.endsWith("_test.dart")) return new Future.value();
+      if (p.split(entry.path).contains('packages')) return new Future.value();
+
+      // TODO(nweiz): Provide a way for the caller to gracefully handle some
+      // isolates failing to load without stopping the rest.
+      return loadFile(entry.path);
+    })).then((suites) => suites.toSet()..remove(null));
+  }
+
+  /// Loads a test suite from the file at [path].
+  ///
+  /// This wil throw a [FileSystemException] if there's no `packages/` directory
+  /// available for [path]. Any other load error will cause an
+  /// [IsolateSpawnException] or a [RemoteException].
+  Future<Suite> loadFile(String path) {
+    // TODO(nweiz): Support browser tests.
+    var packageRoot = _packageRoot == null
+        ? p.join(p.dirname(path), 'packages')
+        : _packageRoot;
+
+    if (!new Directory(packageRoot).existsSync()) {
+      throw new FileSystemException("Directory $packageRoot does not exist.");
+    }
+
+    var receivePort = new ReceivePort();
+    return runInIsolate('''
+import "package:unittest/src/vm_listener.dart";
+
+import "${p.toUri(p.absolute(path))}" as test;
+
+void main(_, Map message) {
+  var sendPort = message['reply'];
+  VmListener.start(sendPort, test.main);
+}
+''', {
+      'reply': receivePort.sendPort
+    }, packageRoot: packageRoot).then((isolate) {
+      _isolates.add(isolate);
+      return receivePort.first;
+    }).then((tests) {
+      return new Suite(path, tests.map((test) {
+        return new IsolateTest(test['name'], test['sendPort']);
+      }));
+    });
+  }
+
+  /// Closes the loader and releases all resources allocated by it.
+  Future close() {
+    for (var isolate in _isolates) {
+      isolate.kill();
+    }
+    _isolates.clear();
+    return new Future.value();
+  }
+}