ladybird/Libraries/LibJS/Tests/classes/class-inheritance.js

test("method inheritance", () => {
  class Parent {
    method() {
      return 3;
    }
  }

  class Child extends Parent {}

  const p = new Parent();
  const c = new Child();
  expect(p.method()).toBe(3);
  expect(c.method()).toBe(3);
});

test("method overriding", () => {
  class Parent {
    method() {
      return 3;
    }
  }

  class Child extends Parent {
    method() {
      return 10;
    }
  }

  const p = new Parent();
  const c = new Child();
  expect(p.method()).toBe(3);
  expect(c.method()).toBe(10);
});

test("parent method reference with super", () => {
  class Parent {
    method() {
      return 3;
    }
  }

  class Child extends Parent {
    method() {
      return super.method() * 2;
    }
  }

  const p = new Parent();
  const c = new Child();
  expect(p.method()).toBe(3);
  expect(c.method()).toBe(6);
});

test("child class access to parent class initialized properties", () => {
  class Parent {
    constructor() {
      this.x = 3;
    }
  }

  class Child extends Parent {}

  const p = new Parent();
  const c = new Child();
  expect(p.x).toBe(3);
  expect(c.x).toBe(3);
});

test("child class modification of parent class properties", () => {
  class Parent {
    constructor() {
      this.x = 3;
    }
  }

  class Child extends Parent {
    change() {
      this.x = 10;
    }
  }

  const p = new Parent();
  const c = new Child();
  expect(p.x).toBe(3);
  expect(c.x).toBe(3);

  c.change();
  expect(c.x).toBe(10);
});

test("inheritance and hasOwnProperty", () => {
  class Parent {
    constructor() {
      this.x = 3;
    }
  }

  class Child extends Parent {
    method() {
      this.y = 10;
    }
  }

  const p = new Parent();
  const c = new Child();
  expect(p.hasOwnProperty("x")).toBeTrue();
  expect(p.hasOwnProperty("y")).toBeFalse();
  expect(c.hasOwnProperty("x")).toBeTrue();
  expect(c.hasOwnProperty("y")).toBeFalse();

  c.method();
  expect(c.hasOwnProperty("x")).toBeTrue();
  expect(c.hasOwnProperty("y")).toBeTrue();
});

test("super constructor call from child class with argument", () => {
  class Parent {
    constructor(x) {
      this.x = x;
    }
  }

  class Child extends Parent {
    constructor() {
      super(10);
    }
  }

  const p = new Parent(3);
  const c = new Child(3);
  expect(p.x).toBe(3);
  expect(c.x).toBe(10);
});