css/css-grid/layout-algorithm/grid-fit-content-percentage.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Grid Layout Test: indefinite percentage in fit-content()</title>
<link rel="author" title="Oriol Brufau" href="mailto:obrufau@igalia.com">
<link rel="help" href="https://drafts.csswg.org/css-grid/#track-sizes" title="7.2.1. Track Sizes">
<meta name="assert" content="Checks that an indefinite percentage in fit-content lets the grid container grow enough to contain the max-content contribution of its grid items.">
<style>
.container {
  width: 200px;
  margin-top: 10px;
}
.grid {
  display: inline-grid;
  background: blue;
}
.item {
  background: orange;
}
.item::before, .item::after {
  content: '';
  float: left;
  width: 50px;
  height: 50px;
}
</style>

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<div id="log"></div>

<script>
"use strict";
function clamp(value, min, max) {
  return Math.max(min, Math.min(max, value));
}
const minContent = 50;
const maxContent = 100;
for (const use_calc of [false, true]) {
  for (const percentage of [0, 50, 75, 100, 150]) {
    const value = use_calc ? `fit-content(calc(0px + ${percentage}%))`
                           : `fit-content(${percentage}%)`;
    const container = document.createElement("div");
    container.className = "container";
    document.body.appendChild(container);
    const grid = document.createElement("div");
    grid.className = "grid";
    grid.style.gridTemplateColumns = value;
    container.appendChild(grid);
    const item = document.createElement("div");
    item.className = "item";
    grid.appendChild(item);
    test(function() {
      const colSize = clamp(percentage * maxContent / 100, minContent, maxContent);
      const height = colSize < maxContent ? maxContent : minContent;
      assert_equals(item.offsetWidth, colSize, "Grid item width");
      assert_equals(item.offsetHeight, height, "Grid item height");
      assert_equals(grid.offsetWidth, maxContent, "Grid container width");
      assert_equals(grid.offsetHeight, height, "Grid container height");
      assert_equals(getComputedStyle(grid).gridTemplateColumns, colSize + "px",
                    "Grid column size");
    }, value);
  }
}
</script>