CODEWITHSUNDEEP
javascriptunit-testingmockingmocha.jssinon
miguelmartinezinf
miguelmartinezinf

Reputation: 40

Unit test a function which has a function with callback (request module)

I am making testing in my NodeJS project and I have the following function I want to unit test:

function myRequest(targetUrl, reqBody) {
  return new Promise((resolve, reject) => {
    request.post(targetUrl, { json: reqBody }, (error, response, body) => {
      if (!error && response.statusCode === 200) {
        resolve(body.transferId);
      } else {
        reject(error || body.description || body);
      }
    });
  });
}

I am using mocha and sinon. How can I test this function?

Firstly, I tested using my own mocked request module for the success scenario. Now, I want to do the error scenario, which could be the post function gets an error. How could I do it without changing or making a new one mock of request (to return an error)? Is is possible?

Upvotes: 0

Views: 829

Answers (1)

Lin Du
Lin Du

Reputation: 102207

Here is the unit test solution, you should use sinon.stub:

E.g. index.ts:

import request from 'request';

export function myRequest(targetUrl, reqBody) {
  return new Promise((resolve, reject) => {
    request.post(targetUrl, { json: reqBody }, (error, response, body) => {
      if (!error && response.statusCode === 200) {
        resolve(body.transferId);
      } else {
        reject(error || body.description || body);
      }
    });
  });
}

index.spec.ts:

import { myRequest } from '.';
import chai from 'chai';
import sinon from 'sinon';
import chaiAsPromised from 'chai-as-promised';
import request from 'request';
chai.use(chaiAsPromised);

const { expect } = chai;

describe('myRequest', () => {
  it('should request success', async done => {
    // @ts-ignore
    const stub = sinon.stub(request, 'post').callsFake((uri, options, callback) => {
      const mResponse = { statusCode: 200 };
      const mBody = { transferId: 1 };
      callback(null, mResponse, mBody);
      done();
    });
    const actualValue = await myRequest('url', {});
    // @ts-ignore
    stub.calledOnceWith('url', { json: {} });
    expect(actualValue).to.eq(1);
    stub.restore();
  });

  it('should throw error use request error', async done => {
    const mError = new Error('Internal server error');
    const mResponse = { statusCode: 500 };
    // @ts-ignore
    const stub = sinon.stub(request, 'post').callsFake((uri, options, callback) => {
      callback(mError, mResponse, null);
      done();
    });
    await expect(myRequest('url', {})).to.be.rejectedWith(mError);
    // @ts-ignore
    stub.calledOnceWith('url', { json: {} });
    stub.restore();
  });

  it('should throw error use body.description as error message', async done => {
    const mResponse = { statusCode: 500 };
    const mBody = { description: 'some error' };
    // @ts-ignore
    const stub = sinon.stub(request, 'post').callsFake((uri, options, callback) => {
      callback(null, mResponse, mBody);
      done();
    });
    await expect(myRequest('url', {})).to.be.rejectedWith(mBody.description);
    // @ts-ignore
    stub.calledOnceWith('url', { json: {} });
    stub.restore();
  });

  it('should throw error use body as error message', async done => {
    const mResponse = { statusCode: 500 };
    const mBody = 'some error';
    // @ts-ignore
    const stub = sinon.stub(request, 'post').callsFake((uri, options, callback) => {
      callback(null, mResponse, mBody);
      done();
    });
    await expect(myRequest('url', {})).to.be.rejectedWith(mBody);
    // @ts-ignore
    stub.calledOnceWith('url', { json: {} });
    stub.restore();
  });
});

Unit test result with 100% coverage:

  myRequest
    ✓ should request success
    ✓ should throw error use request error
    ✓ should throw error use body.description as error message
    ✓ should throw error use body as error message


  4 passing (13ms)

---------------|----------|----------|----------|----------|-------------------|
File           |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
---------------|----------|----------|----------|----------|-------------------|
All files      |      100 |      100 |      100 |      100 |                   |
 index.spec.ts |      100 |      100 |      100 |      100 |                   |
 index.ts      |      100 |      100 |      100 |      100 |                   |
---------------|----------|----------|----------|----------|-------------------|

Source code: https://github.com/mrdulin/mocha-chai-sinon-codelab/tree/master/src/stackoverflow/58822996

Upvotes: 1

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