mochajs/mocha ? reverse-engineered prompt

Build me a reliable JavaScript test framework for Node.js and the browser, something like Mocha.

I want to be able to write tests in a friendly style with describe and it blocks, run them from the command line, and also run the same tests in a browser. It should support the usual test setup and cleanup flow, clean reporting for passing and failing tests, useful error output, and an easy way to run only certain tests when I need to focus on one area.

Please make it feel polished and well tested, with documentation and examples so someone new can get started quickly. If you need to check current docs or best practices online, go ahead. I mainly want the core testing experience to be solid, fast, and dependable for both Node and browser use.