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Simple Yet Powerful Mocking Framework for NodeJs


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nodemock now honors NaN as an argument

Thanks goes to @kibamaple for reporting Issue #8 that this fix release addresses.



A simple Yet Powerful Mocking Framework for NodeJs

NodeMock is a Simple, Yet Powerful Mocking Framework for NodeJs

NodeMock is a very simple to use mocking framework which can be used to mock functions in JavaScript objects. NodeMock creates mock methods in less code with more expressive manner.


Besides it's simplicity it supports following features:

  • Does not need an existing object to create the mock
  • Verify arguments (we check deeply on objects and arrays to check the validity)
  • Allow a return to be sent
  • Assertion to check whether all the rules executed
  • Callbacks can also be executed with providing arguments
  • Multiple mock functions in one object
  • Alter a mock function later on
  • Method chaining allows creating mocks super easy
  • Fail support added when calling method that should not be called
  • Mock support to call a single method more than once
  • Repetitive support
  • Ignore methods from mocking behaviour
  • Ability to provide functions to determine valid input for mocked functions
  • Ability to provide functions to generate output from mocked functions


Node JS can be used with any testing framework. And we've used it with Nodeunit and it's a perfect match. See Examples


npm install nodemock


Load the Module

var nodemock = require("nodemock");

Name a mock for clarity

var mocks = [ nodemock.named('mock1').mock('foo').takes(1), nodemock.named('mock2').mock('foo').takes(1) ], i; for(i = 0; i < mocks.length; i += 1) { mocks[i].assert(); // Prints that «mockName».foo(1) was not called. }

Creating a mock function with taking arguments and return value

var mocked = nodemock.mock("foo").takes(10, [10, 20, 30]).returns(98); mocked.foo(10, [10, 20, 30]); // this will return 98 mocked.foo(10); //throws execption

Creating a mock with callback support

var mocked = nodemock.mock("foo") .takes(20, function(){}) .calls(1, [30, 40]); mocked.foo(20, function(num, arr) { console.log(num); //prints 30 console.log(arr); //prints 40 }); /* When you invoke foo() nodemock will calls the callback(sits in argument index 1 - as specified) with the parameters 30 and 40 respectively. */

Creating a mock function that takes variable parameters

var mocked = nodemock.mock("foo").takes(function(args) { return(args % 2 == 0) }); mocked.foo(4) // works mocked.foo(5) // fails

Creating a mock function that takes variable parameters and returns dynamic values

var mocked = nodemock.mock("foo").takesF(function(args) { return(args % 2 == 0) }).returnsF(function(args) { return(args * 2) }); mocked.foo(4) // returns 8 mocked.foo(5) // fails

Creating a mock with callback support

var mocked = nodemock.mock("foo") .takes(20, function(){}) .calls(1, [30, 40]); mocked.foo(20, function(num, arr) { console.log(num); //prints 30 console.log(arr); //prints 40 }); /* When you invoke foo() nodemock will calls the callback (sits in argument index 1 - as specified) with the parameters 30 and 40 respectively. */

Controlling callbacks

With the asynchronous nature of NodeJS(and brower with AJAX too) it'll be great if we can control the execution of the callback in the testing environment. And ctrl() of nodemock helps that

var ctrl = {}; var mocked = nodemock.mock('foo').takes(10, function() {}).ctrl(1, ctrl); //where ever in your codebase ctrl.trigger(10, 20); // you can call this as many as you want

Add multiple mock functions

var mocked = nodemock.mock("foo").takes(10).returns(30); mocked.foo(10); //gives 30 mocked.mock("bar").takes(true).returns(40); mocked.bar(true); // gives 40

Assertion Support

var mocked = nodemock.mock("foo").takes(20); var mocked = nodemock.mock("bar").takes(40); mocked.foo(20); mocked.bar(40); //check whether what we've defined is actually executed mocked.assert(); //returns true

Fails when calls any method in the mock object

var mocked = nodemock.fail(); mocked.foo(); //throws an exception mocked.bar(); //throws an exception

Fails when calls some particular method in the mock object

var mocked = nodemock.mock("foo").fail(); mocked.mock("bar").takes(10); mocked.foo(); //throws an exception mocked.bar(10); //works perfectly

calls a single mocked method, multiple times

var mocked = nodemock.mock("foo").takes(10, 20).times(2); mocked.foo(10, 20); mocked.foo(10, 20);

calls a single mocked method, multiple times with different returns

var mocked = nodemock.mock("foo").takes(10, 20).returns(100); mocked.mock('foo').takes(10, 20).returns(200); mocked.foo(10, 20); //returns 100 mocked.foo(10, 20); //returns 200

mock a single method more than once

var mocked = nodemock.mock("foo").takes(10, 20); mocked.mock("foo").takes(20, 30); mocked.mock("foo").takes(500); mocked.foo(10, 20); mocked.foo(20, 30) mocked.foo(500); //check whether everything has done mocked.assert(); //returns true

reset the mock

var mocked = nodemock.mock('foo').returns(100); mocked.foo(); //returns 100 mocked.assert(); //returns true mocked.reset(); mocked.mock('doo').returns(300); mocked.doo(); //returns 300 mock.assert() //returns true

ignore method

Sometime we need to ignore some methods going through mocking rules. But we need to have those methods but doing nothing.

var mocked = nodemock.ignore('hello'); mocked.mock('foo').returns(100); mock.foo(); //returns 100 mock.hello(); //do nothing but the method exists mock.assert(); // return true, assert ignores ignored methods

API Documentation


var mocked = require('nodemock').mock('foo'); Creating a object with mock function "foo" mocked.mock(methodName) Used to alter or create a new mock method and add rules to it as usual


mocked.takes(arg1, args2, ...) Specify arguments of the function and verify then when calling mocked.takesF(function) As opposed to takes(), in which we can only specify static values, takesF() (note the "F" in the name to indicate that it takes a function) allows client code to provide a predicate that determines whether the mocked function should accept ("take") the value and allowing mock code to be a bit more dynamic. mocked.takesAll() A shorthand function that tells the mock function to accept any input. mocked.returns(returnValue) Specify the return value of the function mocked.returnsF(function) Similar to takesF(), returnsF() allows to provide a function that will dynamically generate values that will be returned from mock calls. The function will be provided with the parameters that were passed to the mock call. mocked.calls(callbackPosition, argumentsArray) Calls a callback at the arguments in index `callbackPosition` with the arguments specified in the "argumentsArray" when using this you've to define a function signature as a callback in the argument list for a callback at index 2 .takes() function will be as, mocked.takes(10, 20, function(){}) mocked.fail() If calls at very begining afterword any call on the mocked objects will fail. Otherwise current mock method will fails someone called that. mocked.times(repetitiveCount); We can rule the mocked method to be called multiple times with same parameters. Finally we can check that using above assert method; mocked.reset() Reset all the rules and mocks created. And bring mocked object into a stage when it's created mocked.ignore() Ignore Some methods from the mocking behaviour


mocked.assert(); Checks whether rules we've defined using other methods were executed. If all the rules were executed return true, otherwise false mocked.assertThrows(); Same as the mocked.assert() but throws an execption if rules breaks.

Copyright (c) 2011 Arunoda Susiripala

Modifications from the mockingbird fork, Copyright (c) 2013 Oscar Renalias

Remaining copyrights owned by individual contributors.



Last updated on 16 Sep 2015

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