Nested comments.

dart/frog/leg/lib/core.dart

 // Copyright (c) 2011, 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.
 
 void print(var obj) {
   // TODO(ngeoffray): enable when the parser accepts it.
   // obj = obj.toString();
   var hasConsole = JS("bool", @"typeof console == 'object'");
   if (hasConsole) {
     JS("void", @"console.log($0)", obj);
@@ skipping 317 matching lines @@
           '>, actual:<' + actual.toString() + '> fails.');
   }
 
   static void fail(String message) {
     _fail("Expect.fail('" + message + "')");
   }
 
   static void _fail(String message) {
     throw message;
   }
+
+  static void isTrue(var actual) {
+    if (actual === true) return;
+    _fail("Expect.isTrue($actual) fails.");
+  }
 }
 
 class Stopwatch {
   double startMs;
   double elapsedMs;
 
   Stopwatch() {
     elapsedMs = 0.0;
   }
 
@@ skipping 29 matching lines @@
     } else {
       return
         JS("num", @"Math.floor($0 + (Date.now() - $1))", elapsedMs, startMs);
     }
   }
 
   int frequency() {
     return 1000;
   }
 }