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node.jsunit-testingmocha.jsconsole.logsinon-chai

console.log unit test failing under mocha with unknown error


My unit test failing for following code.when I run test i see below result with unknown error.I am not getting how to test second parameter paylod in console.log method.

Test console log()
-----------|----------|----------|----------|----------|-------------------|
File       |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------|----------|----------|----------|----------|-------------------|
All files  |    66.67 |      100 |        0 |    66.67 |                   |
 logger.js |    66.67 |      100 |        0 |    66.67 |                 6 |
-----------|----------|----------|----------|----------|-------------------|
npm ERR! Test failed.  See above for more details.

    //logger.js 
    'use strict';

    const log = (message, payload) => {
      console.log(message, JSON.stringify(payload, null, 2));
    };

    module.exports = { log };
    // log.test.js

    'use strict';

    const chai = require('chai');
    const sinon = require('sinon');
    chai.use(require('sinon-chai'));

    const { expect } = chai;
    const log = require('../../src/logger');

    describe('Test console log()', () => {
      it('should log value in console', () => {
        this.stub = sinon.stub(console, 'log');
        log('test invoked', { option: 1 });
      });
    });

Solution

  • Looks like you just need to destructure your require for logger.js:

    'use strict';
    
    const sinon = require('sinon');
    
    const { log } = require('../../src/logger');  // <= destructuring assignment
    
    describe('Test console log()', () => {
      it('should log value in console', () => {
        const stub = sinon.stub(console, 'log');
        log('test invoked', { option: 1 });
        stub.restore();
        sinon.assert.calledWith(stub, 'test invoked', JSON.stringify({ option: 1 }, null, 2));  // Success!
      });
    });