rewire
Dependency injection for node.js applications.
rewire adds a special setter and getter to modules so you can modify their behaviour for better unit testing. You may
- inject mocks for other modules
- leak private variables
- override variables within the module.
rewire does not 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).
Furthermore rewire comes also with support for various client-side bundlers (see below).
Installation
npm install rewire
Examples
var rewire = require("rewire");
var myModule = rewire("../lib/myModule.js");
myModule.__set__("myPrivateVar", 123);
myModule.__get__("myPrivateVar");
myModule.__set__("fs", {
readFile: function (path, encoding, cb) {
cb(null, "Success!");
}
});
myModule.readSomethingFromFileSystem(function (err, data) {
console.log(data);
});
myModule.__set__({
fs: fsMock,
http: httpMock,
someOtherVar: "hello"
});
myModule.__set__({
console: {
log: function () { }
},
process: {
argv: ["testArg1", "testArg2"]
}
});
myModule.__set__("console.log", function () { });
rewire("./myModule.js") === rewire("./myModule.js");
##API
###rewire(filename): rewiredModule
- filename:
Path to the module that shall be rewired. Use it exactly like require().
###rewiredModule.__set__(name, value)
- name:
Name of the variable to set. The variable should be global or defined with var
in the top-leve scope of the module. - value:
The value to set.
###rewiredModule.__set__(env)
- env:
Takes all keys as variable names and sets the values respectively.
###rewiredModule.__get__(name): value
Returns the private variable.
##Client-Side Bundlers
Since rewire relies heavily on node's require mechanism it can't be used on the client-side without adding special middleware to the bundling process. Currently supported bundlers are:
Please note: Unfortunately the line numbers in stack traces have an offset of +2 (browserify) / +1 (webpack).
This is caused by generated code that is added during the bundling process. I'm working on that ... :)
###browserify
var b = browserify(),
bundleSrc;
b.use(require("rewire").bundlers.browserify);
b.addEntry("entry.js");
bundleSrc = b.bundle();
###webpack
var webpackOptions = {
output: "bundle.js"
};
require("rewire").bundlers.webpack(webpackOptions);
webpack("entry.js", webpackOptions, function () {});