Only load a certain number of test suites at once.

lib/src/executable.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.
 
 // TODO(nweiz): This is under lib so that it can be used by the unittest dummy
 // package. Once that package is no longer being updated, move this back into
 // bin.
 library test.executable;
 
 import 'dart:async';
@@ skipping 302 matching lines @@
 
   mergeStreams(paths.map((path) {
     if (new Directory(path).existsSync()) return loader.loadDir(path);
     if (new File(path).existsSync()) return loader.loadFile(path);
 
     return new Stream.fromIterable([
       new LoadSuite("loading $path", () =>
           throw new LoadException(path, 'Does not exist.'))
     ]);
   })).listen((loadSuite) {
-    group.add(new Future.sync(() async {
-      engine.suiteSink.add(loadSuite);
-
-      var suite = await loadSuite.suite;
-      if (suite == null) return;
-      if (pattern != null) {
-        suite = suite.change(
+    group.add(new Future.sync(() {
+      engine.suiteSink.add(loadSuite.changeSuite((suite) {
+        if (pattern == null) return suite;
+        return suite.change(
             tests: suite.tests.where((test) => test.name.contains(pattern)));
-      }
-
-      engine.suiteSink.add(suite);
+      }));
     }));
   }, onError: (error, stackTrace) {
     group.add(new Future.error(error, stackTrace));
   }, onDone: group.close);
 
   await group.future;
 
   // Once we've loaded all the suites, notify the engine that no more will be
   // coming.
   engine.suiteSink.close();
@@ skipping 70 matching lines @@
       if (description is! Map) return false;
       var path = description["path"];
       if (path is! String) return false;
 
       print("$version (from $path)");
       return true;
 
     default: return false;
   }
 }