bug: Use of worker-farm breaks jest's --runInBand & --max-concurrent-workers options

[hulkish]

Usage of worker-farm in a jest runner:

• breaks jest's --runInBand option
• breaks jest's --max-concurrent-workers option
• jest-worker is already handling the concurrency behavior
• the spawning of child.processes will perplex between jest-worker and worker-farm.
• this actually makes it very dangerous for CI environments

Instead, i recommend:

• dropping usage of worker-farm all together
• use the same approach which jest-runner-eslint is using

[rogeliog]

I agree, we should just migrate to use create-jest-runner cc: @SimenB

[SimenB]

Yup yup! Really straight forward to use 🙂