serenity/Libraries/LibJS/Tests/builtins/Object/Object.preventExtensions.js

describe("correct behavior", () => {
  test("non-object arguments", () => {
    expect(Object.preventExtensions()).toBeUndefined();
    expect(Object.preventExtensions(undefined)).toBeUndefined();
    expect(Object.preventExtensions(null)).toBeNull();
    expect(Object.preventExtensions(true)).toBeTrue();
    expect(Object.preventExtensions(6)).toBe(6);
    expect(Object.preventExtensions("test")).toBe("test");

    let s = Symbol();
    expect(Object.preventExtensions(s)).toBe(s);
  });

  test("basic functionality", () => {
    let o = { foo: "foo" };
    expect(o.foo).toBe("foo");
    o.bar = "bar";
    expect(o.bar).toBe("bar");

    expect(Object.preventExtensions(o)).toBe(o);
    expect(o.foo).toBe("foo");
    expect(o.bar).toBe("bar");

    o.baz = "baz";
    expect(o.baz).toBeUndefined();
  });
});

describe("errors", () => {
  test("defining a property on a non-extensible object", () => {
    let o = {};
    Object.preventExtensions(o);

    expect(() => {
      Object.defineProperty(o, "baz", { value: "baz" });
    }).toThrowWithMessage(TypeError, "Cannot define property baz on non-extensible object");

    expect(o.baz).toBeUndefined();
  });

  test("putting property on a non-extensible object", () => {
    let o = {};
    Object.preventExtensions(o);

    expect(() => {
      "use strict";
      o.foo = "foo";
    }).toThrowWithMessage(TypeError, "Cannot define property foo on non-extensible object");

    expect((o.foo = "foo")).toBe("foo");
    expect(o.foo).toBeUndefined();
  });
});