sinon's restore vs. reset

index.test.js

'use strict';

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

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

const expect = chai.expect;
const sandbox = sinon.createSandbox();

// This is the function we will be unit testing. It accepts a `database` and a `log` object
function initializeSomething(database, log) {
    log.info('About to initialize something very important...');
    database.initialize();
    try {
        database.connect();
        log.info('We just initialized something important.');
    } catch (err) {
        log.error({ err }, 'Something went terribly wrong while initializing something very important!');
    }
}

// One mock object for the database
const database = {
    initialize: function () { /* Do nothing */ },
    connect: function () { /* Do nothing */ }
};

// One mock object for the log
const log = {
    info: sandbox.spy(),
    error: sandbox.spy()
};

describe('Differences between sinon\'s reset and restore', () => {

    afterEach(() => {
        sandbox.restore();
    });

    it('Initializes and connects successfully', () => {
        sandbox.stub(database, 'initialize').returns();
        sandbox.stub(database, 'connect').returns();
        initializeSomething(database, log);

        console.log(`database.initialize was called ${database.initialize.callCount} time(s)`);
        // database.initialize was called 1 time(s)

        console.log(`database.initialize was called ${database.connect.callCount} time(s)`);
        // database.initialize was called 1 time(s)

        console.log(`log.info was called ${log.info.callCount} time(s)`);
        // log.info was called 2 time(s)

        console.log(`log.error was called ${log.error.callCount} time(s)`);
        // log.error was called 0 time(s)


        expect(database.initialize).to.be.calledOnce;
        expect(database.connect).to.be.calledOnce;
        expect(log.info).to.be.calledTwice;
        expect(log.error).to.not.be.called;
    });

    it('Initializes and handles connection errors', () => {
        sandbox.stub(database, 'initialize').returns();
        sandbox.stub(database, 'connect').throws();
        initializeSomething(database, log);

        console.log(`database.initialize was called ${database.initialize.callCount} time(s)`);
        // database.initialize was called 1 time(s)

        console.log(`database.initialize was called ${database.connect.callCount} time(s)`);
        // database.initialize was called 1 time(s)

        console.log(`log.info was called ${log.info.callCount} time(s)`);
        // log.info was called 3 time(s) - wait, what!?

        console.log(`log.error was called ${log.error.callCount} time(s)`);
        // log.error was called 1 time(s)

        expect(database.initialize).to.be.calledOnce;
        expect(database.connect).to.be.calledOnce;
        expect(log.info).to.be.calledOnce; // This assertion will fail! We expect to be called once, not thrice!
        expect(log.error).to.be.calledOnce;
    });
});