kolodny

Visual Regression Testing with Jest

This is a walkthrough of how to set up Visual Regression Testing with Jest for an application created with create-react-app.

The following walkthrough uses React as an example, but the approach should work for any modern frontend library! I assume it can be used with Angular, Vue, Cycle.js and more.

This gist walks you through a create-react-app application as an example of how to set up Visual Regression Testing in Jest using libraries I wrote recently which enable this: jsdom-screenshot, jest-transform-css and jest-transform-file.

kolodny

chrome.proxy.settings.set({
                value: {
                    mode: 'pac_script',
                    pacScript: {
                        data:data
                    }
                },
                scope: 'regular'
            }, function(){
                // console.log('set pac scripts result:',arguments);

kolodny

function cache<Query, Result>(
    factory: (query: Query) => Observable<Result>,
    cache: Map<Query, Result> = new Map()): (query: Query) =>
    Observable<Result> {
  const subject = new Subject<Result>();
  return query => {
    if (cache.has(query)) {
      subject.next(cache.get(query));
    } else {
      factory(query).subscribe(results => {

kolodny

Fully Exhaustive Swift State Machine

The following is a nice Swift pattern to make a vanilla Swift state machine:

class Machine {
  enum State {
    case foo
    case bar(String)
    case baz(Int)

kolodny

In this tutorial we're going to build a set of parser combinators.

What is a parser combinator?

We'll answer the above question in 2 steps

1. what is a parser?
2. and.. what is a parser combinator?

So first question: What is parser?

kolodny

let cache = new Map();
let pending = new Map();

function fetchTextSync(url) {
  if (cache.has(url)) {
    return cache.get(url);
  }
  if (pending.has(url)) {
    throw pending.get(url);
  }

kolodny

'use strict'

// see: https://github.com/nodejs/node/pull/6157

var startTime  = process.hrtime()
var startUsage = process.cpuUsage()

// spin the CPU for 500 milliseconds
var now = Date.now()
while (Date.now() - now < 500)

kolodny

// https://github.com/kolodny/immutability-helper

/** Declaration extension point */
declare namespace ImmutabilityHelper {
    interface CustomOperators<T> {
        /* $someShit?: T */
        /* $moreShit?: T */
    }
}

kolodny

#!/bin/sh

set -euo pipefail

#declare valid arguments here
bar=
baz=

function parse_args() {
    args=()

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module.exports = closer;

function closer(codeString) {
  var lines = codeString.split('\n');
  var lastIndent = 0;
  var currentScope = { indent: 0, children: [] };
  for (lineIndex = 0; lineIndex < lines.length; lineIndex++) {
    var line = lines[lineIndex];
    var currentIndent = /^\s*/.exec(line)[0].length;
    if (/^\s*√\s*$/.test(line)) {