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Dependency injection for node.js applications.

rewire allows you to modify the behaviour of modules for better unit testing. You may

• introduce mocks for other modules
• leak private variables
• override variables within the module
• inject your own scripts

rewire doesnot load the file and eval the contents to emulate node's require mechanism. In fact it uses node's own require to load the module. Thus your module behaves exactly the same in your test environment as under regular circumstances (except your modifications).

Debugging is fully supported.

npm install rewire

For older node versions:
rewire is tested with node 0.6.x. I recommend to run the unit tests viamocha in the rewire-folder beforeusing rewire with older node versions.

varrewire=require("rewire");// rewire acts exactly like require when omitting all other paramsrewire("./myModuleA.js")===require("./myModuleA.js");// = true

// You can introduce your own mocks for modules that are required:rewiredModule=rewire("./myModuleA.js",{"fs":{readFile:function(path,encoding,cb){cb(null,"Success!");}},"../path/to/moduleB.js":myMockForModuleB});// The rewired module will now use your mocks instead of fs// and moduleB.js. Just make sure that the path is exactly as// in myModuleA.js required.

// You can inject your own mocks for internal or global objects.// These injections are only visible within the module.rewiredModule=rewire("./myModuleA.js",null,{console:{log:function(){/* be quiet */}},process:{argv:["some","other","args"]},__filename:"some/other/dir"});// This will inject// var console = {log: function () { /* be quiet */ }};// var process = {argv: ["some", "other", "args"]};// var __filename = "some/other/dir";// at the end of the module.// You can also pass a script to inject at the endrewiredModule=rewire("./myModuleA.js",null,"console.log('hello');");// This will print "hello" when the module loads

// You can expose private variables for unit testsrewiredModule=rewire("./myModuleA.js",null,null,["myVar1","myVar2");// This will inject// module.exports.__ = {myVar1: myVar1, myVar2: myVar2}// at the end of the module.// You can access now your private variables under the special.__-objectconsole.log(rewiredModule.__.myVar1);console.log(rewiredModule.__.myVar2);

// You can disable caching of the rewired module. Any require()-calls will// now return the original module again instead of the rewired.// Caching is enabled by default.rewire("./myModuleA.js",null,null,null,false)===require("./myModuleA.js");// = false// You can also delete all rewired modules from the cache by one call.rewire.reset();// You should call this after every unit test to ensure a clean test environment.

##API

rewire(filename, mocks, injections, leaks, cache)

• {!String} filename:
  Path to the module that shall be rewired. Use it exactly like require().

• {Object} mocks (optional):
  An object with module mocks. Keys should reflect the required path of the module.

• {Object|String} injections (optional):
  If you pass an object, all keys of the object will bevars within the module. You can also eval a string.

• {Array<String>} leaks (optional):
  An array with variable names that should be exported. These variables are accessible viamyModule.__.

• {Boolean=true} cache (optional):
  Indicates whether the rewired module should be cached by node so subsequent calls ofrequire() willreturn the rewired module. Further calls ofrewire() will always overwrite the cache.

Returns the rewired module.

rewire.reset()

Removes all rewired modules fromrequire.cache. Everyrequire() will now return the original module again.

So if you writerequire("../../myModules/myModuleA.js") you need to pass{"../../myModules/myModuleA.js": myModuleAMock}.

So if there is any code in your module that is executed duringrequire(), yourinjected variables will be undefined at this point.

Imaginerewire("./myModule.js", null, {console: null});:

console.log("Hello");// ouch, that won't work. console is undefined at this point because of hoisting// End of module ///////////////// rewire will inject herevarconsole=null;

All variables, that arecopied by valuewill not be updated anymore.

A good approach to solve this would be:

varmyLeaks={};module.exports=function(someValue){myLeaks.someValue=someValue;};

And then:rewire("myModuleA.js", null, null, ["myLeaks"]);

BecausemyLeaks is defined at the end of the module, you're able to access the leak object and all leaks thatare attached to it later during runtime.

Allrequire()s will now return the original module again.

This module is inspired by the greatinjectr-module.

(The MIT License)

Copyright (c) 2012 Johannes Ewald <mail@johannesewald.de>

Permission is hereby granted, free of charge, to any person obtaininga copy of this software and associated documentation files (the'Software'), to deal in the Software without restriction, includingwithout limitation the rights to use, copy, modify, merge, publish,distribute, sublicense, and/or sell copies of the Software, and topermit persons to whom the Software is furnished to do so, subject tothe following conditions:

The above copyright notice and this permission notice shall beincluded in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OFMERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANYCLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THESOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.