require-inject

require-inject

A simple mock injector compatible needing no instrumentation in the libraries being tested

Example

var requireInject = require('require-inject');

var mymod = requireInject('mymod', {
    'fs' => {
        stat: function (file,cb) {
            switch (file) {
            case 'testfile1': return cb(null,{})
            case 'testfile2': return cb(new Error('ENOENT'))
            }
        }
    }
})

var myglobal = requireInject.installGlobally('myglobal', { … })

Usage in your tests

• var mymod = requireInject( module, mocks )

module is the name of the module you want to require. This is what you'd pass to require to load the module from your script. This means that for relative paths, the path should be relative to your test script, not to the thing you're injecting dependencies into.

mocks is an object with keys that are the names of the modules you want to mock and values of the mock version of the objects.

requireInject makes it so that when module is required, any of its calls to require for modules inclued in mocks will return the mocked version. It takes care to not impact any other uses of module, any calls to require for it will get a version without mocks.

• var mymod = requireInject.withEmptyCache(module, mocks)

As with requireInject but your require cache will be cleared before requring the module to have mocks injected into it. This can be useful when your test shares dependencies with the module to be mocked and you need to mock a transitive dependency of one of those dependencies. That is:

Test → A → B

ModuleToTest → A → MockedB

If we we didn't clear the cache then ModuleToTest would get the already cached version of A and the MockedB would never be injected. By clearing the cache first it means that ModuleToTest will get it's own copy of A which will then pick up any mocks we defined.

Previously to achieve this you would need to have provided a mock for A, which, if that isn't what you were testing, could be frustrating busy work.

• var myglobal = requireInject.installGlobally( module, mocks)

As with requireInject, except that the module and its mocks are left in the require cache and any future requires will end up using them too. This is helpful particularly in the case of things that defer loading (that is, do async loading).

• var myglobal = requireInject.installGlobally.andClearCache(module, mocks)

As with requireInject.installGlobally but clear the cache first as with requireInject.withEmptyCache. Because this globally clears the cache it means that any requires after this point will get fresh copies of their required modules, even if you required them previously.

Changelog

v1.4.3 (2018-05-04)

Mocked module will now actually be an instance of Module (thanks @jdalton!)

When the code loaded via requireInject resulted in readable-stream being loaded anywhere down the require chain would produce failures in readable-stream's instanceof checks resulting in crashes. This has been worked around by preloading readable-stream when it is available. This won't fix 100% of cases but it will fix the problem most of the time. If it doesn't fix it for you, try adding readable-stream as a dev dep.