test_defineLazyPrototypeGetter.js

Enable keyboard shortcuts

/* Any copyright is dedicated to the Public Domain.

   http://creativecommons.org/publicdomain/zero/1.0/ */

"use strict";

// Test DevToolsUtils.defineLazyPrototypeGetter

function Class() {}

DevToolsUtils.defineLazyPrototypeGetter(Class.prototype, "foo", () => []);

function run_test() {

  test_prototype_attributes();

  test_instance_attributes();

  test_multiple_instances();

  test_callback_receiver();

function test_prototype_attributes() {

  // Check that the prototype has a getter property with expected attributes.

  const descriptor = Object.getOwnPropertyDescriptor(Class.prototype, "foo");

  Assert.equal(typeof descriptor.get, "function");

  Assert.equal(descriptor.set, undefined);

  Assert.equal(descriptor.enumerable, false);

  Assert.equal(descriptor.configurable, true);

function test_instance_attributes() {

  // Instances should not have an own property until the lazy getter has been

  // activated.

  const instance = new Class();

  Assert.ok(!instance.hasOwnProperty("foo"));

  instance.foo;

  Assert.ok(instance.hasOwnProperty("foo"));

  // Check that the instance has an own property with the expecred value and

  // attributes after the lazy getter is activated.

  const descriptor = Object.getOwnPropertyDescriptor(instance, "foo");

  Assert.ok(descriptor.value instanceof Array);

  Assert.equal(descriptor.writable, true);

  Assert.equal(descriptor.enumerable, false);

  Assert.equal(descriptor.configurable, true);

function test_multiple_instances() {

  const instance1 = new Class();

  const instance2 = new Class();

  const foo1 = instance1.foo;

  const foo2 = instance2.foo;

  // Check that the lazy getter returns the expected type of value.

  Assert.ok(foo1 instanceof Array);

  Assert.ok(foo2 instanceof Array);

  // Make sure the lazy getter runs once and only once per instance.

  Assert.equal(instance1.foo, foo1);

  Assert.equal(instance2.foo, foo2);

  // Make sure each instance gets its own unique value.

  Assert.notEqual(foo1, foo2);

function test_callback_receiver() {

  function Foo() {}

  DevToolsUtils.defineLazyPrototypeGetter(Foo.prototype, "foo", function () {

    return this;

});

  // Check that the |this| value in the callback is the instance itself.

  const instance = new Foo();

  Assert.equal(instance.foo, instance);