round-queue-all-tests.js

var chai = require('chai'),
    expect = chai.expect,
    should = chai.should();

var RoundQueue = require('<round-queue-implementation>');

describe('Round-Queue', function(){

    describe('When adding elements', function(){

        it('Should add an element to the end of a non-full queue', function(){
            // Queue with max size of 3
            var nonFullQueue = new RoundQueue(3),
                originalSize,
                poppedElement; 

            originalSize = nonFullQueue.size;

            poppedElement = nonFullQueue.push(1);

            // When the queue is not full, no popping will be done
            expect(poppedElement).to.be.undefined;
            
            // Element should've been added to the end of the queue
            nonFullQueue.last().should.be.equal(1)
            // Size should've been increased by 1
            nonFullQueue.size.should.be.equal(originalSize + 1);
        });

        it('Should pop the first element and add the new element to the end of a full queue', function(){
            var fullQueue = new RoundQueue(3),
                originalSize,
                poppedElement;

            fullQueue.push(1);
            fullQueue.push(2);
            fullQueue.push(3); // Queue is now full

            originalSize = fullQueue.size;

            poppedElement = fullQueue.push(4);

            // The first element should've been popped
            poppedElement.should.be.equal(1);
            // The second element should've been shifted to the first position
            fullQueue.first().should.be.equal(2);
            // The new element should've been added to the end of the queue
            fullQueue.last().should.be.equal(4);
            // The size shouldn't have changed
            fullQueue.size.should.be.equal(originalSize);
        });

    });

    describe('When removing elements', function(){

        it('Should remove the first element of a non-empty queue', function(){
            var nonEmptyQueue = new RoundQueue(3),
                originalSize,
                poppedElement;

            nonEmptyQueue.push(1);
            nonEmptyQueue.push(2);

            originalSize = nonEmptyQueue.size;

            poppedElement = nonEmptyQueue.pop();

            // The first elements should've been popped
            poppedElement.should.be.equal(1);

            // The second element should've been shifted to the first position
            nonEmptyQueue.first().should.be.equal(2);

            // The size should've been decreased by 1
            nonEmptyQueue.size.should.be.equal(originalSize - 1);
        });

        it('Should throw an error on an empty queue', function(){
            var emptyQueue = new RoundQueue(3);

            expect(emptyQueue.pop).to.throw(Error);
        });

    });
});