Run each test case in a separate process / better isolated context?

Do you want to request a feature or report a bug?

Request a feature.

What is the current behavior?

Currently, tests in a single test source file are run one after the other in the same process / context. One can use resetModules and resetMocks (disabled by default!?) to reduce the chances of one test to affect another test.

One of the problems with resetModules and resetMocks is that this doesn’t jive very well with having ES6’ top-level import declarations in your test source file. They create references to the initial module / mock instances that resetModules and resetMocks won’t be able to “reset” to new instances. Someone had already filed a ticket for that in the past: https://github.com/facebook/jest/issues/3236

Instead of trying to reset the state after each test case (which is hard!), I think it’s better to run each test case in “true isolation” in a separate node.js process (or perhaps a lighter way of isolating, I’m not sure what it would be though).

Please provide your exact Jest configuration and mention your Jest, node, yarn/npm version and operating system.

Using:

• Jest v22.2.2
• Node v8.9.1
• Yarn v1.3.2

[sseletskyy-apixio]

jest has a built in flat to run all tests sequentially

jest --runInBand

alias -i

I used that for running just test against storybook+puppeteer environment (e.g. npm lib spdt)

[hugollm]

I actually needed this for some tests with puppeteer. I’m probably better off refactoring the setup or test logic, but meanwhile I got isolation with:

jest --listTests | xargs -L 1 -P 0 jest

This runs each file as a separate jest command, so each of my test files spawn a new puppeteer context, solving my problem for now. Figured I would post this here in case it helps someone.