How to write a Jest configuration file

Question

I am trying to pass along a configuration file to Jest in order to run tests only from a given directory.

According to documentation, you can use config.testPathDi

Answer 1

As of the current date of October 5, 2018, I was able to setup a jest configuration file with ease, without it requiring it to be in JSON format.

My package.json scripts section:

"scripts": {
    "start": "node server.js",
    "dev": "webpack-dev-server --hot --inline",
    "test": "jest --config ./jest-config.js",
    "build": "webpack",
    "postinstall": "webpack"
  }

I decided to keep the jest-config file in the root path alongside package.json, so that's where it is pointing to, but you can put it anywhere you want. Here is the configuration file, albeit a little short:

module.exports = {
  verbose: true,
  setupTestFrameworkScriptFile: "./enzyme.js",
  roots: [
    "../__tests__"
  ],
  modulePaths: [
    "./__stubs__"
  ],
  moduleNameMapper: {
    ".scss$": "scss-stub.js"
  }
}

The Jest documentation in the "Configuring Jest" section (link here) says that you can create it with a module.exports object. They include a caveat that says, "Please keep in mind that the resulting configuration must be JSON-serializable", which adds to the confusion. "Delightful Javascript Testing!" Hah!

P.S. The roots property in the config tells Jest where to look for all of your tests. Thought it might help.