(function() {
  class SyncTestZoneSpec implements ZoneSpec {
    runZone = Zone.current;

    constructor(namePrefix: string) {
      this.name = 'syncTestZone for ' + namePrefix;
    }

    // ZoneSpec implementation below.

    name: string;

    onScheduleTask(delegate: ZoneDelegate, current: Zone, target: Zone, task: Task): Task {
      switch (task.type) {
        case 'microTask':
        case 'macroTask':
          throw new Error(`Cannot call ${task.source} from within a sync test.`);
        case 'eventTask':
          task = delegate.scheduleTask(target, task);
          break;
      }
      return task;
    }
  }

  // Export the class so that new instances can be created with proper
  // constructor params.
  Zone['SyncTestZoneSpec'] = SyncTestZoneSpec;
})();