describe('stack', () => {
  it('should push item to the top of the stack', () => {
    // implement test here:
    // 1. require the stack
    // 2. create stack push calls to place some items in the stack
    // 3. write assertions via the expect() API
  });

  it('should pop the item from the top of stack', () => {
    // implement test here:
    // 1. require the stack
    // 2. create stack push calls to place some items in the stack
    // 3. pop a few items off the stack
    // 4. write assertions via the expect() API
  });
});