kata.js

// 48: Set - add
// To do: make all tests pass, leave the assert lines unchanged!

describe('`add()` appends a new element to the end of a Set object.', function(){

  let set;
  beforeEach(() => set = new Set());

  it('adds every value, of any type, only once', function() {
    const fn = () => {};

    set.add(1);
    set.add(1);
    set.add(fn);
    set.add({fn});

    assert.equal(set.size, 2);
  });

  it('is chainable', function() {
    set.add.add;

    assert.equal(set.has(2), true);
  });

  it('call without params adds undefined', function() {
    set.add

    assert.equal(set.has(void 0), true);
  });

  it('0, -0 and +0 are equal', function() {
    set.add();
    set.add();

    assert.equal(set.has(+0), true);
  });
});