text: 'use strict';
  
  self.getterRejects = (t, obj, getterName, target) => {
    const getter = Object.getOwnPropertyDescriptor(obj, getterName).get;
  
    return promise_rejects_js(t, TypeError, getter.call(target), getterName + ' should reject with a TypeError');
  };
  
  self.getterRejectsForAll = (t, obj, getterName, targets) => {
    return Promise.all(targets.map(target => self.getterRejects(t, obj, getterName, target)));
  };
  
  self.methodRejects = (t, obj, methodName, target, args) => {
    const method = obj[methodName];
  
    return promise_rejects_js(t, TypeError, method.apply(target, args),
                              methodName + ' should reject with a TypeError');
  };
  
  self.methodRejectsForAll = (t, obj, methodName, targets, args) => {
    return Promise.all(targets.map(target => self.methodRejects(t, obj, methodName, target, args)));
  };
  
  self.getterThrows = (obj, getterName, target) => {
    const getter = Object.getOwnPropertyDescriptor(obj, getterName).get;
  
    assert_throws_js(TypeError, () => getter.call(target), getterName + ' should throw a TypeError');
  };
  
  self.getterThrowsForAll = (obj, getterName, targets) => {
    targets.forEach(target => self.getterThrows(obj, getterName, target));
  };
  
  self.methodThrows = (obj, methodName, target, args) => {
    const method = obj[methodName];
    assert_equals(typeof method, 'function', methodName + ' should exist');
  
    assert_throws_js(TypeError, () => method.apply(target, args), methodName + ' should throw a TypeError');
  };
  
  self.methodThrowsForAll = (obj, methodName, targets, args) => {
    targets.forEach(target => self.methodThrows(obj, methodName, target, args));
  };
  
  self.constructorThrowsForAll = (constructor, firstArgs) => {
    firstArgs.forEach(firstArg => assert_throws_js(TypeError, () => new constructor(firstArg),
                                                   'constructor should throw a TypeError'));
  };
  
  self.garbageCollect = () => {
    if (self.gc) {
      // Use --expose_gc for V8 (and Node.js)
      // Exposed in SpiderMonkey shell as well
      self.gc();
    } else if (self.GCController) {
      // Present in some WebKit development environments
      GCController.collect();
    } else {
      /* eslint-disable no-console */
      console.warn('Tests are running without the ability to do manual garbage collection. They will still work, but ' +
        'coverage will be suboptimal.');
      /* eslint-enable no-console */
    }
  };
  
  self.delay = ms => new Promise(resolve => step_timeout(resolve, ms));
  
  // For tests which verify that the implementation doesn't do something it shouldn't, it's better not to use a
  // timeout. Instead, assume that any reasonable implementation is going to finish work after 2 times around the event
  // loop, and use flushAsyncEvents().then(() => assert_array_equals(...));
  // Some tests include promise resolutions which may mean the test code takes a couple of event loop visits itself. So go
  // around an extra 2 times to avoid complicating those tests.
  self.flushAsyncEvents = () => delay(0).then(() => delay(0)).then(() => delay(0)).then(() => delay(0));
  