queue.spec.js

import 'mocha';
import { expect } from 'chai';
import Queue from '../../../src/js/data-structures/queue';

describe('Queue', () => {
  let queue;

  beforeEach(() => {
    queue = new Queue();
  });

  it('starts empty', () => {
    expect(queue.size()).to.equal(0);
    expect(queue.isEmpty()).to.equal(true);
  });

  it('enqueues elements', () => {
    queue.enqueue(1);
    expect(queue.size()).to.equal(1);
    queue.enqueue(2);
    expect(queue.size()).to.equal(2);
    queue.enqueue(3);
    expect(queue.size()).to.equal(3);

    expect(queue.isEmpty()).to.equal(false);
  });

  it('dequeue elements', () => {
    queue.enqueue(1);
    queue.enqueue(2);
    queue.enqueue(3);

    expect(queue.dequeue()).to.equal(1);
    expect(queue.dequeue()).to.equal(2);
    expect(queue.dequeue()).to.equal(3);
    expect(queue.dequeue()).to.equal(undefined);
  });

  it('implements FIFO logic', () => {
    queue.enqueue(1);
    expect(queue.peek()).to.equal(1);
    queue.enqueue(2);
    expect(queue.peek()).to.equal(1);
    queue.enqueue(3);
    expect(queue.peek()).to.equal(1);

    expect(queue.dequeue()).to.equal(1);
    expect(queue.dequeue()).to.equal(2);
    expect(queue.dequeue()).to.equal(3);
    expect(queue.dequeue()).to.equal(undefined);
  });

  it('allows to peek at the front element in the queue without dequeuing it', () => {
    expect(queue.peek()).to.equal(undefined);

    queue.enqueue(1);
    expect(queue.peek()).to.equal(1);

    queue.enqueue(2);
    expect(queue.peek()).to.equal(1);

    queue.dequeue();
    expect(queue.peek()).to.equal(2);
  });

  it('returns the correct size', () => {
    expect(queue.size()).to.equal(0);
    queue.enqueue(1);
    expect(queue.size()).to.equal(1);
    queue.enqueue(2);
    expect(queue.size()).to.equal(2);
    queue.enqueue(3);
    expect(queue.size()).to.equal(3);

    queue.clear();
    expect(queue.isEmpty()).to.equal(true);

    queue.enqueue(1);
    queue.enqueue(2);
    queue.enqueue(3);
    expect(queue.size()).to.equal(3);

    queue.dequeue();
    expect(queue.size()).to.equal(2);
    queue.dequeue();
    expect(queue.size()).to.equal(1);
    queue.dequeue();
    expect(queue.size()).to.equal(0);
    queue.dequeue();
    expect(queue.size()).to.equal(0);
  });

  it('returns if it is empty', () => {
    expect(queue.isEmpty()).to.equal(true);
    queue.enqueue(1);
    expect(queue.isEmpty()).to.equal(false);
    queue.enqueue(2);
    expect(queue.isEmpty()).to.equal(false);
    queue.enqueue(3);
    expect(queue.isEmpty()).to.equal(false);

    queue.clear();
    expect(queue.isEmpty()).to.equal(true);

    queue.enqueue(1);
    queue.enqueue(2);
    queue.enqueue(3);
    expect(queue.isEmpty()).to.equal(false);

    queue.dequeue();
    expect(queue.isEmpty()).to.equal(false);
    queue.dequeue();
    expect(queue.isEmpty()).to.equal(false);
    queue.dequeue();
    expect(queue.isEmpty()).to.equal(true);
    queue.dequeue();
    expect(queue.isEmpty()).to.equal(true);
  });

  it('clears the queue', () => {
    queue.clear();
    expect(queue.isEmpty()).to.equal(true);

    queue.enqueue(1);
    queue.enqueue(2);
    expect(queue.isEmpty()).to.equal(false);

    queue.clear();
    expect(queue.isEmpty()).to.equal(true);
  });

  it('returns toString primitive types', () => {
    expect(queue.toString()).to.equal('');

    queue.enqueue(1);
    expect(queue.toString()).to.equal('1');

    queue.enqueue(2);
    expect(queue.toString()).to.equal('1,2');

    queue.clear();
    expect(queue.toString()).to.equal('');

    const queueString = new Queue();
    queueString.enqueue('el1');
    expect(queueString.toString()).to.equal('el1');

    queueString.enqueue('el2');
    expect(queueString.toString()).to.equal('el1,el2');
  });

  it('returns toString objects', () => {
    class MyObj {
      constructor(el1, el2) {
        this.el1 = el1;
        this.el2 = el2;
      }
      toString() {
        return `${this.el1.toString()}|${this.el2.toString()}`;
      }
    }
    const queueMyObj = new Queue();
    expect(queueMyObj.toString()).to.equal('');

    queueMyObj.enqueue(new MyObj(1, 2));
    expect(queueMyObj.toString()).to.equal('1|2');

    queueMyObj.enqueue(new MyObj(3, 4));
    expect(queueMyObj.toString()).to.equal('1|2,3|4');
  });
});