Node.js axios unit testing using Mocha, sinon and chai

Question

I have node.js component name controller.js which have a function that calls api service using axios with options and it also have catch function for error handling. I am not able to stub axios function so as to cover it by unit testing.

Below is controller.js component.

const axios = require('axios');
export.getData = function(req, res, next) {
  try {
     const options = {
            method: 'GET',
            headers: headers,
            url,
            params: queryParams
     };  
     axios(options).then(function (response) {
            res.json(response.data);
        })
            .catch(function (error) {
                if (error && error.response) {
                    if (error.response.status === 401) {
                        res.status(500).send({ error: true, message: 'There seems to be an issue, please try after sometime' });                   
                    }
                 }
             });
  }
}

below is my controller.test.js

const chai = require('chai');
const assert = chai.assert;
const axios = require('axios');
const sinon = require('sinon');
const controller = require('../controllersr');

describe("controller API testing", () => {

it("should call getMarketId function and return status 200 on success", function (done) {
        const req = { };
        const res =  { json: {greet: "hello"}, status: 200};
        var mockStub = sinon.stub(axios, 'get').resolves(res);
        controller.getData(req, res);
        assert.equal(res.status, 200);
        mockStub.restore();
        done();
    });

});

Here, I am not able to stub axios funtion and catch function for error handling. And thus unable to cover the code for axios success and catch function in NYC. Please help..

Answer 1

First, You can't use try...catch statement to catch asynchronous code, if you want to do so, you need to use async/await to wait for the promise to be resolved or rejected. Besides, since you already caught the axios exception and didn't re-throw it, you don't need to try...catch .

Second, you are trying to stub axios function which is a standalone function imported from axios module. Sinon does NOT support that. You need to use Link Seams , so we will be using proxyquire to construct our seams.

Eg

controller.js :

const axios = require('axios');

exports.getData = function (req, res, next) {
  const options = {
    method: 'GET',
    headers: headers,
    url,
    params: queryParams,
  };
  axios(options)
    .then(function (response) {
      res.json(response.data);
    })
    .catch(function (error) {
      if (error && error.response) {
        if (error.response.status === 401) {
          res.status(500).send({ error: true, message: 'There seems to be an issue, please try after sometime' });
        }
      }
    });
};

controller.test.js :

const sinon = require('sinon');
const proxyquire = require('proxyquire');

describe('controller API testing', () => {
  it('should call getMarketId function and return status 200 on success', async () => {
    const req = {};
    const res = { json: sinon.stub(), status: 200 };
    const axiosStub = sinon.stub().resolves({ data: { greet: 'hello' } });
    const controller = proxyquire('./controller', {
      axios: axiosStub,
    });
    await controller.getData(req, res);
    sinon.assert.calledWithExactly(axiosStub, {
      method: 'GET',
      headers: {},
      url: 'http://localhost:3000/api',
      params: {},
    });
    sinon.assert.calledWithExactly(res.json, { greet: 'hello' });
  });
});

unit test result:

  controller API testing
    ✓ should call getMarketId function and return status 200 on success (1306ms)


  1 passing (1s)

---------------|---------|----------|---------|---------|-------------------
File           | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
---------------|---------|----------|---------|---------|-------------------
All files      |    62.5 |        0 |   66.67 |    62.5 |                   
 controller.js |    62.5 |        0 |   66.67 |    62.5 | 15-17             
---------------|---------|----------|---------|---------|-------------------