test("length is 1", () => {
  expect(Reflect.preventExtensions).toHaveLength(1);
});

describe("errors", () => {
  test("target must be an object", () => {
    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
      expect(() => {
        Reflect.preventExtensions(value);
      }).toThrowWithMessage(
        TypeError,
        "First argument of Reflect.preventExtensions() must be an object"
      );
    });
  });
});

describe("normal behavior", () => {
  test("properties cannot be added", () => {
    var o = {};
    o.foo = "foo";
    expect(Reflect.preventExtensions(o)).toBeTrue();
    o.bar = "bar";
    expect(o.foo).toBe("foo");
    expect(o.bar).toBeUndefined();
  });

  test("property values can still be changed", () => {
    // FIXME: This doesn't work even though it should (the value remains unchanged)
    // var o = {};
    // o.foo = "foo";
    // expect(Reflect.preventExtensions(o)).toBeTrue();
    // o.foo = "bar";
    // expect(o.foo).toBe("bar");
  });
});