Add tests for stack chains in the browser.

test/chain/utils.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.
+
+library stack_trace.test.chain.utils;
+
+import 'dart:async';
+
+import 'package:stack_trace/stack_trace.dart';
+import 'package:test/test.dart';
+
+/// Runs [callback] in a microtask callback.
+void inMicrotask(callback()) => scheduleMicrotask(callback);
+
+/// Runs [callback] in a one-shot timer callback.
+void inOneShotTimer(callback()) => Timer.run(callback);
+
+/// Runs [callback] once in a periodic timer callback.
+void inPeriodicTimer(callback()) {
+  var count = 0;
+  new Timer.periodic(new Duration(milliseconds: 1), (timer) {
+    count++;
+    if (count != 5) return;
+    timer.cancel();
+    callback();
+  });
+}
+
+/// Runs [callback] within a long asynchronous Future chain.
+void inFutureChain(callback()) {
+  new Future(() {})
+      .then((_) => new Future(() {}))
+      .then((_) => new Future(() {}))
+      .then((_) => new Future(() {}))
+      .then((_) => new Future(() {}))
+      .then((_) => callback())
+      .then((_) => new Future(() {}));
+}
+
+void inNewFuture(callback()) {
+  new Future(callback);
+}
+
+void inSyncFuture(callback()) {
+  new Future.sync(callback);
+}
+
+/// Returns a Future that completes to an error using a completer.
+///
+/// If [trace] is passed, it's used as the stack trace for the error.
+Future completerErrorFuture([StackTrace trace]) {
+  var completer = new Completer();
+  completer.completeError('error', trace);
+  return completer.future;
+}
+
+/// Returns a Stream that emits an error using a controller.
+///
+/// If [trace] is passed, it's used as the stack trace for the error.
+Stream controllerErrorStream([StackTrace trace]) {
+  var controller = new StreamController();
+  controller.addError('error', trace);
+  return controller.stream;
+}
+
+/// Runs [callback] within [asyncFn], then converts any errors raised into a
+/// [Chain] with [Chain.forTrace].
+Future<Chain> chainForTrace(asyncFn(callback()), callback()) {
+  var completer = new Completer();
+  asyncFn(() {
+    // We use `new Future.value().then(...)` here as opposed to [new Future] or
+    // [new Future.sync] because those methods don't pass the exception through
+    // the zone specification before propagating it, so there's no chance to
+    // attach a chain to its stack trace. See issue 15105.
+    new Future.value().then((_) => callback())
+        .catchError(completer.completeError);
+  });
+  return completer.future
+      .catchError((_, stackTrace) => new Chain.forTrace(stackTrace));
+}
+
+/// Runs [callback] in a [Chain.capture] zone and returns a Future that
+/// completes to the stack chain for an error thrown by [callback].
+///
+/// [callback] is expected to throw the string `"error"`.
+Future<Chain> captureFuture(callback()) {
+  var completer = new Completer<Chain>();
+  Chain.capture(callback, onError: (error, chain) {
+    expect(error, equals('error'));
+    completer.complete(chain);
+  });
+  return completer.future;
+}