Dject Dynamic Double Loader

A simple tool for building test doubles. The Dject Dynamic Double Loader allows you to create injectable dependencies which are easy to consume and easy to use in your tests. It's actually harder to write about how this works than to just demonstrate it!

Installation

In your project run this:

npm i dject-dynamic-double-loader --save-dev

Done!

Using it

Writing a Test Double

If you use Dject to load your test doubles, the loader works a little like this:

(This example was pulled from a real test double! Sinon usage not required, but it sure makes testing easier!)

function textFileServiceFake(
    djectDynamicDoubleLoader,
    sinon
) {
    'use strict';

    // Yes, this is really all you need to create a fully injectible test double!
    return djectDynamicDoubleLoader
        .buildDjectTestDouble('textFileService')
        .appendProperty('readJsonFile', sinon.stub())
        .appendProperty('writeTextFile', sinon.stub());
}

module.exports = textFileServiceFake;

If you don't want to do it this way, here's what you can do instead:

const djectDynamicDoubleLoader = require('dject-dynamic-double-loader');
const sinon = require('sinon');

module.exports = djectDynamicDoubleLoader
    .buildDjectTestDouble('textFileService')
    .appendProperty('readJsonFile', sinon.stub())
    .appendProperty('writeTextFile', sinon.stub());

Seriously, I couldn't make this easier.

Using your Test Double

Once you are down to writing your test, it just looks like this:

const container = require('../container');
const testContainer = require('./testContainer');

describe('doing some testing', function () {
    let importDIBuilder;
    let textFileServiceFake;

    beforeEach(function () {
        const appContainer = container.new();

        const someFakeData = testContainer.build('someFakeData');

        // No, seriously, this is it! All the code lives in the test double file
        textFileServiceFake = testContainer.build('textFileServiceFake');
        textFileServiceFake.readJsonFile.callsFake(() => someFakeData);

        appContainer.register(textFileServiceFake);

        importDIBuilder = appContainer.build('importDIBuilder');
    });

    it('connects the dots, la la lala', function() {
        // your test code goeth here.
    });
});

Version History

v1.0.0

Initial commit - Introduced core functionality:

• djectDynamicDoubleLoader.buildDjectTestDouble(string)
• testDouble.appendProperty(string, any)