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require-expose-plugin

expose! dependencies for your tests

require-expose-plugin is a RequireJS loader plugin to expose dependency module references for stubbing/mocking/spying purposes in unit tests. It provides a means to access the loaded dependecies for a target module by prepending the module path with 'expose!'.

src/my-dependency.js - a dependency

define(function() {
  return {
    bar: function(greeting) {
      console.log(greeting);
    }
  };
});

src/my-module.js - a module

define(['src/my-dependency'], function(dependency) {
  return {
    foo: function(salutation, name) {
      dependency.bar(salutation + ', ' + name);
    }
  };
});

spec/my-module.spec.js - a test

define(['expose!src/my-module'], function(myModule)) {

  describe('My Module', function() {
    var dependency = myModule.require_exposed_dependencies['src/my-dependency'];
    
    spyOn(dependency, 'bar');
    myModule.foo('hello', 'world');
    expect(dependency).toHaveBeenCalledWith('hello, world');
  });
  
});

How It Works

The require-expose-plugin first loads the target module file as a plain text file, then runs a RegEx to grab the associated dependencies, require()'s those dependencies and builds a reference map using the resource path as the key. That map is then added as a new property to the target module: require_exposed_dependencies.

Using the resource path, you can access that dependency just as if you had declared it as a dependency for the current module.

From the example above, you have access to the 'src/my-dependency' module without declaring it within the define() dependencies of the my-module.spec:

var dependency = myModule.require_exposed_dependencies['src/my-dependency'];

The example utilizes Jasmine to spy on src/my-dependency:bar, but you can choose whichever unit testing framework you like. require-expose-plugin does not utilize any specific unit testing framework; it simply exposes dependency references.

[note] Just be aware that if the unit testing framework you choose modifies the object when wrapping for stub/mock/spy, that you unwrap on teardown or before exiting the expectation as it may leave side affects for other modules who do not want to have the dependency wrapped.

Intent

The intent of require-expose-plugin is to aid in stubbing/mocking/spying a dependency module of a target resource module. Dependency references, themselves, are not exposed on a module by RequireJS. As such, using the expose! loader plugin will allow access to dependencies by adding a property to the target module: require_exposed_dependencies.

It is not the intent of expose! to be used in the wild on a production-level application/site. Not saying it can't be; not guarenteeing it. As well, I feel that it's use for such purpose other than to stub/mock/spy for testing defeats the methodology of modular development. Not to say that using expose! to access dependencies other than to stub/mock/spy is inherently wrong... just a little smelly.

Caveats

require-expose-plugin utilizes Array.prototype.indexOf and XMLHttpRequest. As such, it is only supported in all modern browsers/runtime-environments and IE9+.