How to run Jest tests sequentially?

Question

CLI options are documented and also accessible by running the command jest --help.

You'll see the option you are looking for : --runInBand.

I'm still getting familiar with Jest, but it appears that describe blocks run synchronously whereas test blocks run asynchronously. I'm running multiple describe blocks within an outer describe that looks something like this:

describe
    describe
        test1
        test2

    describe
        test3

In this case, test3 does not run until test2 is complete because test3 is in a describe block that follows the describe block that contains test2.

It worked for me ensuring sequential running of nicely separated to modules tests:

1) Keep tests in separated files, but without spec/test in naming.

|__testsToRunSequentially.test.js
|__tests
   |__testSuite1.js
   |__testSuite2.js
   |__index.js

2) File with test suite also should look like this (testSuite1.js):

export const testSuite1 = () => describe(/*your suite inside*/)

3) Import them to testToRunSequentially.test.js and run with --runInBand:

import { testSuite1, testSuite2 } from './tests'

describe('sequentially run tests', () => {
   testSuite1()
   testSuite2()
})

Use the serial test runner:

npm install jest-serial-runner --save-dev

Set up jest to use it, e.g. in jest.config.js:

module.exports = {
   ...,
   runner: 'jest-serial-runner'
};

You could use the project feature to apply it only to a subset of tests. See https://jestjs.io/docs/en/configuration#projects-arraystring--projectconfig