Is there a way to run some tests sequentially with Jest?

Question

Jest runs your test suite in parallel by default, but there is a flag (--runInBand) that allows you to run the whole suite sequentially (as pointed out here)

Answer 1

Extended from Joachim Lous's answer, you can divide test files into projects and specify a different runner for each project.

In jest.config.js:

module.exports = {
  projects: [
    {
      displayName: "default-tests",
      testEnvironment: "node",
    },
    {
      displayName: "serial-tests",
      testEnvironment: "node",
      runner: "jest-serial-runner",
      testMatch: ["**/?(*.)+(serial-test).[jt]s?(x)"],
    },
  ],
}

Then, rename any tests that need to be run sequentially to *.serial-test.js (as opposed to *.test.js).