Javascript FizzBuzz and Behavior-Driven Development Using Mocha and Chai

Question

I am currently getting closely acquainted with Behavior-Driven Development. Could someone tell me how I am doing with the Fizzbuzz program below? I am interested in both improving the JavaScript code and the BDD prowess. Any help is appreciated.

fizzbuzz.js

module.exports = function(word, value){   
    function sortNumber(a,b) {
        return a - b;
    }
    
    numbers = function(divisor, max){
        var result = []
        for(i=1;i<=max;i++){
            if ((i % divisor) === 0)
                result.push(i)
        }
        return result
    }
    
    if (value <= 0)
        return ['error','nonpositive']
        
    else {
        switch(word) {
            case 'fizz':
                return numbers(3, value)
            case 'buzz':
                return numbers(5,value)
            case 'fizzbuzz':
                return numbers(3,value).concat(numbers(5,value)).filter(function(elem,index,self){
                        return index == self.indexOf(elem)
                    }).sort(sortNumber)
            default:
                return ['error','wrongword']
        }
    }
};

test/fizzbuzz-spec.js:

var chai = require('chai');
    expect = chai.expect,
    fizzbuzz = require('../lib/fizzbuzz');
    
describe('A fizzbuzz', function(){
    describe('will return an error for invalid words: ', function(){
        it('like fuss', function(){
            expect(fizzbuzz('fuss', 10)).to.be.deep.equal(['error','wrongword']);
        });
        it('like biss', function(){
            expect(fizzbuzz('biss', 10)).to.be.deep.equal(['error','wrongword']);
        });
    });
    
    describe('will return an error when non-positive integer is passed', function(){
        it('like 0', function(){
            expect(fizzbuzz('buzz', 0)).to.be.deep.equal(['error','nonpositive']);
        })
        it('like -2', function(){
            expect(fizzbuzz('buzz', -2)).to.be.deep.equal(['error','nonpositive']);
        })
    })
    
    describe('will return valid non-error input when positive integers and valid words are passed', function(){
        it('like fizz and 20', function(){
            expect(fizzbuzz('fizz', 20)).not.to.contain('error');
        })
        it('like buzz and 20', function(){
            expect(fizzbuzz('buzz', 20)).not.to.contain('error');
        })
        it('like fizzbuzz and 20', function(){
            expect(fizzbuzz('fizzbuzz', 20)).not.to.contain('error');
        })      
    })
    
    describe('will return valid results for some basic valid test cases', function(){
        it('like fizz and 10', function(){
            expect(fizzbuzz('fizz', 10)).to.be.deep.equal([3,6,9]);
        })
        it('like fizz and 20', function(){
            expect(fizzbuzz('fizz', 20)).to.be.deep.equal([3,6,9,12,15,18]);
        })
        it('like buzz and 10', function(){
            expect(fizzbuzz('buzz', 10)).to.be.deep.equal([5,10]);
        })
        it('like buzz and 25', function(){
            expect(fizzbuzz('buzz', 25)).to.be.deep.equal([5,10,15,20,25]);
        })
        it('like fizzbuzz and 10', function(){
            expect(fizzbuzz('fizzbuzz', 10)).to.be.deep.equal([3,5,6,9,10]);
        })
        it('like fizzbuzz and 25', function(){
            expect(fizzbuzz('fizzbuzz', 25)).to.be.deep.equal([3,5,6,9,10,12,15,18,20,21,24,25]);
        })
        it('like fizz and 2', function(){
            expect(fizzbuzz('fizz', 2)).to.be.deep.equal([]);
        })
        it('like buzz and 4', function(){
            expect(fizzbuzz('buzz', 4)).to.be.deep.equal([]);
        })
        
    })
});

Sᴀᴍ Onᴇᴌᴀ · Accepted Answer · 2020-08-13 16:34:09Z

Handling invalid input

Instead of returning an array when inputs are invalid, throw exceptions and use throw to detect it in the tests.

Avoid `else` when previous blocks have return statements

The else can be eliminated since the block evaluated when value <= 0 has a return statement (or would throw an exception). Additionally, the switch statement can be simplified to a few if statements (for an example see this answer to a related question).

Don't forget to set scopes

While the code is in a module, it is best to set the scope of variables and functions - e.g. numbers and i in the loop within numbers should be prefixed by the keywords const and let, respectively, to avoid accidental re-assignment/confusion.

In that same vein, the first few lines of the test are setting variables:

var chai = require('chai');
    expect = chai.expect,
    fizzbuzz = require('../lib/fizzbuzz');

Perhaps you meant to add a comma instead of semi-colon after require('chai')? It would be simpler just to have each variable on its own line:

const chai = require('chai');
const expect = chai.expect;
const fizzbuzz = require('../lib/fizzbuzz');

Actually instead of importing chai just to use expect from it on a separate line, use object-destructuring:

const { expect } = require('chai');
const fizzbuzz = require('../lib/fizzbuzz');

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Javascript FizzBuzz and Behavior-Driven Development Using Mocha and Chai

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Handling invalid input

Avoid `else` when previous blocks have return statements

Don't forget to set scopes

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Javascript FizzBuzz and Behavior-Driven Development Using Mocha and Chai

1 Answer 1

Handling invalid input

Avoid else when previous blocks have return statements

Don't forget to set scopes

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Related

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Avoid `else` when previous blocks have return statements