Expressmocks NPM

expressmocks

A small utility to write unit tests for Express request handlers in a more readable and shorter fashion, based on Sinon.JS and promises.

While this libary is written with Mocha, Sinon and Chai in mind, it should also work with other testing frameworks.

It's written in TypeScript and provides declaration files, but should also work with Babel or plain ES6+.

Installation

Prerequisites:

npm install -D sinon

To install:

npm install -D expressmocks

Usage examples

Let's say you have the following SampleEndpoints implementation:

import { RequestHandler } from 'express'

const helloWorld: RequestHandler = (req, res, next) => {
    const { name } = req.params

    if (name === 'Carsten') {
        res.status(200).send(`Hello ${name}`)
    } else if (name) {
        res.status(404).send()
    } else {
        next(new Error('validation failed'))
    }
}

Some simple tests look like this:

import { ExpressMocks } from 'expressmocks'
import { helloWorld } from './SampleEndpoints'

describe('helloWorld', () => {
    it('should say hello to Carsten', () => {
        return ExpressMocks.create({ params: { name: 'Carsten' } }).test(helloWorld)
            .expectStatus(200)
            .expectSend('Hello Carsten')
    })

    it('should return with 404 for others', () => {
        return ExpressMocks.create({ params: { name: 'Simon' } }).test(helloWorld)
            .expectStatus(404)
            .expectSend()
    })

    it('should fail via next() on validation error', () => {
        return ExpressMocks.create().test(helloWorld)
            .expectNext(Error, 'validation failed')
    })
})

ExpressMocks creates stubs for the request, response and next parameters and provides a simple API to test against the most often used method calls.

The functions of the request and response objects are SinonJS stubs, which can be checked via regular Sinon API. You may also add your own custom stubs if you are using some more esoteric functionality:

    it('should allow testing on missing `cork()` method', () => {
        return ExpressMocks.create({}, { cork: sinon.stub() })
            .test((req, res, next) => {
                res.cork()
                // ...
            })
            .expectEnd()
            .then(({ res }) => {
                // using chai & sinon-chai
                expect(res.writeHead).to.have.been.called
                expect(res.cork).to.have.been.called
            })
    })

For more examples, please see the sample project and the ExpressMocksSpec