verify arguments to serries / parallel functions

lib/createParallel.js

@@ -2,11 +2,12 @@
 
 var _ = require('lodash');
 var async = require('async');
+var verifyArguments = require('./verifyArguments');
 
 function createParallel(mapFn){
 
  function buildParallel(){
- var args = _.flatten(arguments);
+ var args = verifyArguments(_.flatten(arguments));
 
  function parallel(done){
  async.map(args, mapFn, done);

lib/createSeries.js

@@ -2,11 +2,12 @@
 
 var _ = require('lodash');
 var async = require('async');
+var verifyArguments = require('./verifyArguments');
 
 function createSeries(mapFn){
 
  function buildSeries(){
- var args = _.flatten(arguments);
+ var args = verifyArguments(_.flatten(arguments));
 
  function series(done){
  async.mapSeries(args, mapFn, done);

lib/verifyArguments.js

@@ -0,0 +1,13 @@
+var assert = require('assert');
+
+module.exports = function(args){
+
+ assert(args.length > 0, 'A set of functions to combine is mandatory');
+
+ args.forEach(function(arg, argIdx){
+ assert.equal(typeof arg, 'function',
+ 'Only functions can be combined, got ' + typeof arg + ' for argument ' + argIdx);
+ });
+
+ return args;
+};

test/verifyArguments.js

@@ -0,0 +1,32 @@
+'use strict';
+
+var test = require('tap').test;
+
+var verifyArguments = require('../lib/verifyArguments');
+
+function validArg() {
+}
+
+test('should act as pass-through for a valid set of arguments', function(t){
+ var args = [validArg, validArg];
+ t.deepEqual(verifyArguments(args), args);
+ t.end();
+});
+
+test('should throw descriptive error message on invalid argument', function(t){
+ t.throws(function(){
+ verifyArguments([validArg, 'invalid', validArg]);
+ }, {
+ name: 'AssertionError', message: 'Only functions can be combined, got string for argument 1'
+ }, 'should throw AssertionError');
+ t.end();
+});
+
+test('should throw descriptive error message on when no arguments provided', function(t){
+ t.throws(function(){
+ verifyArguments([]);
+ }, {
+ name: 'AssertionError', message: 'A set of functions to combine is mandatory'
+ }, 'should throw AssertionError');
+ t.end();
+});