If you want to migrate Jasmine tests to Jest, jest-codemods helps you a lot. I used it in a project with more than 200 tests, and it slashed the effort by several days:
The tool is going to ask you a few questions. Here are the correct answers for a standard Angular project:
? Which parser do you want to use?
? Which test library would you like to migrate from?
! Jasmine: globals
? Are you using the global object for assertions (i.e., without requiring them)?
! Yes, and I'm not afraid of false positive transformations
? Will you be using Jest on Node.js as your test runner?
! Yes, use the globals provided by Jest (recommended)
The tool doesn't fix every incompatiblity. Luckily, most issues are pretty obvious. Richard Wotzlaw has written a deep dive on migrating to Jest, including list of replacements.