Rick Wong RickWong

Idiomatic React Testing Patterns

Testing React components seems simple at first. Then you need to test something that isn't a pure interaction and things seem to break down. These 4 patterns should help you write readable, flexible tests for the type of component you are testing.

Setup

I recommend doing all setup in the most functional way possible. If you can avoid it, don't set variables in a beforeEach. This will help ensure tests are isolated and make things a bit easier to reason about. I use a pattern that gives great defaults for each test example but allows every example to override props when needed:

Micro Post: Sneaky Arrow Functions

I was just hacking away on a side project when I wrote this code:

const screencastMock = {
  findOne: () => { }
};

	The question was asked why I (as a programmer who prefers dynamic languages) don't consider static types "worth it". Here
	is a short list of what I would need from a type system for it to be truely useful to me:

	1) Full type inference. I would really prefer to be able to write:

	(defn concat-names [person]
	(assoc person :full-name (str (:first-name person)
	(:second-name person))))

	And have the compiler know that whatever type required and produced from this function was acceptible as long as the

	/*<?php
	///public class PhpJava { public static void main(String[] args) { System.out.printf("/%s",
	//\u000A\u002F\u002A
	class PhpJava {
	static function main() {
	echo(//\u000A\u002A\u002F
	"Hello World!");
	}}
	//\u000A\u002F\u002A
	PhpJava::main();

	var INIT = '@redux/INIT'

	function createStore (reducer, state, enhancer) {
	if (enhancer) return enhancer(createStore)(reducer, state)

	var subscribers = []

	dispatch({ type: INIT })

	return {

	<html>
	<body>
	<div id="react-root"></div>

	<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-with-addons.js"></script>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.js"></script>
	<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/redux/3.5.2/redux.js"></script>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.7.7/babel.min.js"></script>
	<script id="react-app" type="text/template">
	const App = ({name}) => {

	const App = ({name}) => {
	return (
	<h1>Hello {name}</h1>
	);
	};

	ReactDOM.render(<App name="World" />, document.getElementById("App"));

	module ImperativeQuickSort (quicksort) where

	import Prelude hiding (take,drop,length,tail,init)
	import Data.Vector (modify,Vector)
	import Data.Vector.Generic.Mutable hiding (modify)

	-- \| Imperative quicksort with O(log n) auxilary space (on top of returned vector)
	quicksort :: Ord a => Vector a -> Vector a
	quicksort = modify qsort'
	where

	import numpy as np
	import hashlib

	def create_block(parent_block, value, hashfunc):
	""" ------------------------------------------------
	String -> Block -> (Block -> String) -> Block
	------------------------------------------------
	Produce a new block from a string value and a hash
	of its parent block. In this case, a block is also a string.
	"""

	// paste in your console
	speechSynthesis.onvoiceschanged = function() {
	var msg = new SpeechSynthesisUtterance();
	msg.voice = this.getVoices().filter(v => v.name == 'Cellos')[0];
	msg.text = Object.keys(window).join(' ');
	this.speak(msg);
	};