When it comes to testing legacy code, there's no one-size-fits-all approach. Two prominent software developers, Michael Feathers and Tim Bray, offer differing perspectives on the topic. According to Feathers, starting with an experiment that requires tests for every change helps teams discover better code and improve their workflow. On the other hand, Bray suggests that some people prefer implementing behavior first and then writing tests, as long as the result is a correct program with robust tests.

Source: https://bitfieldconsulting.com/posts/testing-legacy-code