Writing clear, readable test assertions is crucial for maintainable test suites that accurately verify application behavior. With over 12 years of Node.js development experience since 2014 and as the creator of CoreUI, I’ve written thousands of test assertions for production APIs. Chai is an assertion library that provides multiple assertion styles (expect, should, assert) with chainable, natural language syntax. This approach creates tests that read like documentation and clearly express what is being tested.