Npm Mocha Libraries

When are Mocha Libraries Useful

Mocha is a flexible library providing developers the ability to create asynchronous test cases in a simple and fun manner. Mocha libraries are particularly useful for:

• Testing asynchronous code: Due to its robust handling of asynchronous code, Mocha is highly beneficial for testing Node.js callback routes, promises, or async/await. Mocha allows flexibility to check if asynchronous operations complete correctly or not.
• TDD (Test Driven Development) or BDD (Behavior Driven Development): Mocha is setup-agnostic which means it supports any setup, making it a keen player in both TDD and BDD.
• For client-side and server-side testing: Mocha can run both in Node.js and in the browser which means it has various applications from testing simple JavaScript utilities to checking server outputs on endpoints.

What Functionalities do Mocha Libraries Usually Have

Mocha has several key functionalities out of the box that extend past what some testing libraries offer:

1. Synchronous and Asynchronous testing: Mocha provides robust testing features to handle both synchronous and asynchronous code.
2. Hooks: Mocha provides hooks like before, after, beforeEach, afterEach which are executed in a structured manner aligning along your test cases. These are used to set preconditions and clean up after tests.
3. Reporters: Mocha has fantastic reporting, with spec, dot matrix, list, progress, JSON, minimal, and other outputs for test results.
4. Interface options: Mocha gives you the choice to choose your style of DSL either BDD describe, it, before, after; TDD suite, test, setup, teardown or exports exports.before, exports.after and so on.

Gotchas/Pitfalls to Look Out For

Despite Mocha's user-friendly build, there are a few things to watch out for when using the library:

• Returning Promises: Mocha can often hang if you don't return your promises. Make sure to always return your promises so Mocha knows to wait for them.
• Global variable leaks: Mocha won't clean up or isolate your tests, which means it could lead to global leaks. Ensure that your tests clean up after themselves.
• Timeouts: Be aware that mocha's default timeout is 2000ms. For longer asynchronous operations, you may need to increase the timeout using this.timeout().
• Arrow Functions: Using arrow functions, () => {}, can prove problematic. Mocha discourages them because they lexically bind this and can't access the Mocha context. It's recommended to use function expressions instead.