assertion library for Node.js

 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.