Yes we're using the built-in test runner and it's much better than jest.

Jest is full of unneeded magic (= complexity), whereas node:test is straightforward and has a better design. Highly recommended. You can turn off process isolation for extra speedup!

How large is your project?

Without process isolation we got 6x speedup vs. jest! But it is difficult to ensure a clean slate between our test suites (~40 suites which all use a test DB)

We are also using some helpers to mock, e.g https://github.com/marchaos/jest-mock-extended - its such helper libraries im concerned about.

Process isolation is an absolute non-negotiable must for any seriously sized project (>50 developers) I’ve worked on