Fix mocha lint

circle.yml

 machine:
   node:
     version: 6
+
+test:
+  pre:
+    - npm run lint

test/.eslintrc.js

+module.exports = {
+    'env': {
+      'mocha': true,
+    },
+};

test/helpers/package-json.js

@@ -2,25 +2,26 @@ const expect = require('chai').expect;
 const fs = require('fs');
 const packageJson = require('../../app/helpers/package-json');
 const winston = require('winston');
+
 packageJson.setLogger(winston);
 
 const inputContent = fs.readFileSync('./test/_fixtures/package.json/inputs/01.json', 'utf8');
 
-describe('package.json helper', function() {
-  describe('setNewValue', function() {
-    it('replaces a dependency value', function() {
+describe('package.json helper', () => {
+  describe('setNewValue', () => {
+    it('replaces a dependency value', () => {
       const outputContent = fs.readFileSync('./test/_fixtures/package.json/outputs/011.json', 'utf8');
       const testContent =
         packageJson.setNewValue(inputContent, 'dependencies', 'cheerio', '0.22.1');
       expect(testContent).to.equal(outputContent);
     });
-    it('replaces only the first instance of a value', function() {
+    it('replaces only the first instance of a value', () => {
       const outputContent = fs.readFileSync('./test/_fixtures/package.json/outputs/012.json', 'utf8');
       const testContent =
         packageJson.setNewValue(inputContent, 'devDependencies', 'angular-touch', '1.6.1');
       expect(testContent).to.equal(outputContent);
     });
-    it('replaces only the second instance of a value', function() {
+    it('replaces only the second instance of a value', () => {
       const outputContent = fs.readFileSync('./test/_fixtures/package.json/outputs/013.json', 'utf8');
       const testContent =
         packageJson.setNewValue(inputContent, 'devDependencies', 'angular-sanitize', '1.6.1');