Add a filesystem descriptor library to scheduled_test.

pkg/scheduled_test/lib/src/utils.dart

Index: pkg/scheduled_test/lib/src/utils.dart
diff --git a/pkg/scheduled_test/lib/src/utils.dart b/pkg/scheduled_test/lib/src/utils.dart
index b5e086e4c11b38c34d64e255f8fe590bf28d004a..e36863d19bba0f1de8c428e72be965986ebcc0b9 100644
--- a/pkg/scheduled_test/lib/src/utils.dart
+++ b/pkg/scheduled_test/lib/src/utils.dart
@@ -24,3 +24,39 @@ Future pumpEventQueue([int times=200]) {
   if (times == 0) return new Future.immediate(null);
   return new Future.immediate(null).then((_) => pumpEventQueue(times - 1));
 }
+
+/// Returns whether [iterable1] has the same elements in the same order as
+/// [iterable2]. The elements are compared using `==`.
+bool orderedIterableEquals(Iterable iterable1, Iterable iterable2) {
+  var iter1 = iterable1.iterator;
+  var iter2 = iterable2.iterator;
+
+  while (true) {
+    var hasNext1 = iter1.moveNext();
+    var hasNext2 = iter2.moveNext();
+    if (hasNext1 != hasNext2) return false;
+    if (!hasNext1) return true;
+    if (iter1.current != iter2.current) return false;
+  }
+}
+
+// TODO(nweiz): remove this when issue 8731 is fixed.
+/// Returns a [Stream] that will immediately emit [error] and then close.
+Stream errorStream(error) => new Future.immediateError(error).asStream();
+
+/// Returns a buffered stream that will emit the same values as the stream
+/// returned by [future] once [future] completes. If [future] completes to an
+/// error, the return value will emit that error and then close.
+Stream futureStream(Future<Stream> future) {
+  var controller = new StreamController();
+  future.then((stream) {
+    stream.listen(
+        controller.add,
+        onError: (error) => controller.signalError(error),
+        onDone: controller.close);
+  }).catchError((e) {
+    controller.signalError(e);
+    controller.close();
+  });
+  return controller.stream;
+}