feat(helpers): add promisify method

promisify method converts callback style methods to promises

package.json

@@ -7,9 +7,9 @@
     "lint": "standard",
     "pretest": "npm run lint",
     "posttest": "npm run coverage",
-    "test:local": "node ./node_modules/.bin/japa",
+    "test:local": "node --harmony-async-await ./node_modules/.bin/japa",
     "test": "./node_modules/.bin/nyc npm run test:local",
-    "test:win": "node ./node_modules/japa-cli/index.js",
+    "test:win": "node --harmony-async-await ./node_modules/japa-cli/index.js",
     "coverage": "nyc report --reporter=text-lcov | coveralls"
   },
   "keywords": [

src/Helpers/index.js

@@ -10,6 +10,7 @@
 */
 
 const path = require('path')
+const pify = require('pify')
 
 /**
  * The Adonis framework is the core module containing all the required
@@ -166,6 +167,20 @@ class Helpers {
   tmpPath (toFile = '') {
     return path.join(this._appRoot, '/tmp', toFile)
   }
+
+  /**
+   * Promisify callback style functions
+   *
+   * @method promisify
+   *
+   * @param  {Function} fn
+   * @param  {Object}   options
+   *
+   * @return {Promise}
+   */
+  promisify (fn, options) {
+    return pify(fn, options)
+  }
 }
 
 module.exports = Helpers

test/helpers.spec.js

@@ -11,6 +11,7 @@
 
 const test = require('japa')
 const path = require('path')
+const fs = require('fs')
 
 const Helpers = require('../src/Helpers')
 
@@ -74,4 +75,9 @@ test.group('Helpers', (group) => {
   test('return path to a file inside tmp dir', (assert) => {
     assert.equal(this.helpers.tmpPath('logs.txt'), path.join(__dirname, './tmp/logs.txt'))
   })
+
+  test('promisify callback style functions', async (assert) => {
+    const readFile = this.helpers.promisify(fs.readFile)
+    await readFile(path.join(__dirname, '../package.json'))
+  })
 })