As someone who eschewed jest and others for years for the simplicity of mocha, I still appreciate the design decision of mocha to keep the assertions library separate from the test harness. Which is to point out that chai [1] is still a great assertions library and only an assertions library.
(I haven't had much problem with TypeScript config in node:test projects, but partly because "type": "module" and using various versions of "erasableSyntaxOnly" and its strict-flag and linter predecessors, some of which were good ideas in ancient mocha testing, too.)