Test color algorithms

color-test.js

// uses mocha
const { rgb } = require("wcag-contrast");
const fromHex = require("@fantasy-color/from-hex").default;
const fs = require("fs");
const assert = require("assert");

const parsedColors = fs
  .readFileSync(__dirname + "/../parsed-colors.txt")
  .toString()
  .split("\n")
  .map(colors => colors.split(" "));

function isDarkColor(color) {
  const [r, g, b] = hexToRGBArray(color);
  const yiq = (r * 299 + g * 587 + b * 114) / 1000;
  // Note: the value 150 is hardcoded into GitHub
  return yiq < 150;
}

const oldMethod = color => (isDarkColor(color) ? "#000000" : "#ffffff");

function yc(color) {
  const t = "string" == typeof color ? parseInt(color.replace("#", ""), 16) : color;
  return +((299 * ((t >> 16) & 255) + 587 * ((t >> 8) & 255) + 114 * (255 & t)) / 1e3 / 255).toFixed(2) < 0.6
    ? "#ffffff"
    : "#000000";
}

const hexToRGBArray = color => {
  const { red, green, blue } = fromHex(color);
  return [red, green, blue];
};

const calcFontColor = color => {
  const blackContrastScore = rgb(hexToRGBArray(color), [0, 0, 0]);
  const whiteContrastScore = rgb(hexToRGBArray(color), [255, 255, 255]);

  return blackContrastScore >= whiteContrastScore ? "#000000" : "#ffffff";
};

it("wcag method", () => {
  let misses = 0;
  parsedColors.forEach(([color, expectedColor]) => {
    if (calcFontColor(color) !== expectedColor) {
      misses++;
    }
  });
  assert.equal(misses, 0);
});

it("oldMethod", () => {
  let misses = 0;
  parsedColors.forEach(([color, expectedColor]) => {
    if (oldMethod(color) !== expectedColor) {
      misses++;
    }
  });
  assert.equal(misses, 0);
});

it("yc", () => {
  let misses = 0;
  parsedColors.forEach(([color, expectedColor]) => {
    if (yc(color) !== expectedColor) {
      misses++;
    }
  });
  assert.equal(misses, 0);
});

test-results.txt

mocha test/color-alg-test.js


  1) wcag method
  2) oldMethod
  3) yc

  0 passing (31ms)
  3 failing

  1) wcag method:

      AssertionError [ERR_ASSERTION]: 29 == 0
      + expected - actual

      -29
      +0
      
      at Context.it (test/color-alg-test.js:47:10)

  2) oldMethod:

      AssertionError [ERR_ASSERTION]: 2903 == 0
      + expected - actual

      -2903
      +0
      
      at Context.it (test/color-alg-test.js:57:10)

  3) yc:

      AssertionError [ERR_ASSERTION]: 1049 == 0
      + expected - actual

      -1049
      +0
      
      at Context.it (test/color-alg-test.js:67:10)