Use Mocha and Chai for Unit Test

Install Mocah and Chai

npm install mocha --save
npm install chai --save

Test Fucntions

Change test scripts in package.json to following:

  "scripts": {
    "test": "mocha"
  },

app.js

module.exports = {
  sayHello: function(){
    return 'hello';
  },
  addNumbers: function(val1, val2){
    return val1 + val2;
  }
}

appTest.js

const assert = require('chai').assert;
const app = require('../app');

sayHelloResult = app.sayHello();
addNumbersResult = app.addNumbers(5, 5);

describe('App', function(){
  describe('sayHello', function(){
    it('sayHello should return hello', function(){
      assert.equal(sayHelloResult, 'hello');
    });

    it('sayHello should return string', function(){
      assert.typeOf(sayHelloResult, 'string');
    });
  });

  describe('addNumbers', function(){
    it('addNumbers should be above 5', function(){
      assert.isAbove(addNumbersResult, 5);
    });

    it('addNumbers should return type number', function(){
      assert.typeOf(addNumbersResult, 'number');
    });
  });
});