Jest controls mocks by placing the mock object in the mocks directory of the directory which the mock target exists. In this case esdb.js is in the db directory so the structure looks like this:

./db/esdb.js
./db/mocks/esdb.js

In my test case file I put the following code: jest.mock(‘../db/esdb’) This line tells Jest to use the mock implementation of esdb rather than the real implementation of esdb. What I have been doing is commenting out the the jest.mock() line while developing so that my test cases execute against my real local implementation of EventStore. What I want to do is make this a switchable option so that I do not have to comment out all jest.mock lines when I want to switch from the mock implementation rather than the real implementation. Unfortunately, but rightly so, Jest validates all cli inputs. So it is not easy to use a command line switch. Something like the following would be nice:

npm test --unmockAll

I did see a blog post showing how to do this but it seemed like a lot of work to achieve when using an environment variable achieves the same goal and is a lot less work. What I did instead was add the following the test.json file in my config directory.

    "testConfig" : {
    "unmockAll": false
}

Then change the const ESDB = require() to var ESDB = require() and add the following lines after the jest.mock

jest.mock('../db/esdb');
if(config.hasOwnProperty("testConfig") && config.testConfig.hasOwnProperty("unmockAll") && config.testConfig.unmockAll) {
    ESDB = jest.requireActual('../db/esdb');
}

Yes, getting this mock setup and working correctly has a lot of work and it feels unnecessary. I’m quite convinced that I will be able to refactor this project to not have to use mocks for I/O utilities like EventStore or Grpc. Those are well tested and well supported software packages so no need to include them in my unit tests.