Bdtjtk

I started writing unit tests for my nodeJs application so i could learn about this concept.
After writing some basic tests for simple functions (using Mocha and Chai) i want to move on to some more complex tests.

I have written a simple piece of code that can make a request using node's HTTPS module. That code looks like this:

const https = require('https')

 module.exports.doRequest = function (params, postData) {

  return new Promise((resolve, reject) => {

    const req = https.request(params, (res) => {

      let body = 

      res.on('data', (chunk) => {

        body.push(chunk)

      })

      res.on('end', () => {

        try {

          body = JSON.parse(Buffer.concat(body).toString())

        } catch (e) {

          reject(e)

        }

        resolve(body)

      })

    })

    req.on('error', (err) => {

      reject(err)

    })

    if (postData) {

      req.write(JSON.stringify(postData))

    }

    req.end()

  })

}

Now i want to invoke this method with the following parameters:

const PARAMS = {

    host: 'jsonplaceholder.typicode.com',

    port: 433,

    method: 'GET',

    path: `/todos/1`,

    headers: {

      Authorization: 'Bearer 123'

    }

}

And make the request like so:

getTodos = (PARAMS) => {

  return doRequest(PARAMS).then((result) => {

    if (result.errors) { throw result }

    return {

      'statusCode': 200,

      'body': JSON.stringify({ message: result.title }),

    }

  }).catch((error) => ({

      'statusCode': error.statusCode,

      'body': JSON.stringify({ message: error.message }),

    }

  ))

}

Now my question is how i can test this bit of code properly. I have looked on how to tackle this with the Nock.js libary but i don't have a good understanding on where to start.
If anyone can point me in the right direction on how to start with writing some tests for this bit of code i will be thankfull.

In general, you would want to black box your HTTP handling, so that as few modules in your application need to care about the details of HTTP as possible.

In the source folder, you'd have one module (e.g. commonhttp.js). You want this to export your HTTP functions, and other modules in your application use them like this:

const commonhttp = require('./commonhttp');

commonhttp.doRequest( ... ).then( ... );

Other modules, like todos.js, and various other modules, will export their own functions using that module, for example:

const commonhttp = require('./commonhttp');



const todos = {

    getTodos( ... ) {

        return commonhttp.doRequest( ... );

    },



    createTodo( ... ) {

        return commonhttp.doRequest( ... );

    },



    // etc.

};



module.exports = todos;

For your unit tests, when you test the todos.js module, you want to mock any calls to the commonhttp module; you can use simple mocha + Sinon for this, and spy on the doRequest method. Basically all you're testing is "when I call getTodos, I expect it to make a call to doRequest with these arguments". You'd follow this pattern for all the modules in your application that uses doRequest.

You also, of course, want to test the commonhttp module -- that spec is where Nock might come in handy. It's not strictly necessary, you can also "block-box" the http module, but you have to set up a lot of complicated spies to mimic the behavior of http; instead, writing a spec (using Nock) that says "ok, I call doRequest with these params, that should have made this HTTP call" does make sense.