Chai is a BDD / TDD assertion library for Node.js and the browser that can be delightfully paired with any javascript testing framework. This library is test framework agnostic.

Test-driven development (TDD) is a software development process that relies on the repetition of a very short development cycle: requirements are turned into very specific test cases, then the software is improved to pass the new tests

BDD of Behavior-Driven Development is an extension of test-driven development that makes use of a simple, domain-specific scripting language (DSL). These DSLs convert structured natural language statements into executable tests.

Node.js is an event-based server-side JavaScript engine.