f (!x.endsWith('px'))
    return NaN;
  return parseFloat(x);
}

const testCases = ['before', 'after', 'backdrop'];
const elements = testCases.map(testCase => document.querySelector('.' + testCase));
const asyncTests = testCases.map(
    testCase => async_test(`ch in pseudo-element ::${testCase} should be recalculated after loading a web font`));

// Before loading custom font, tests should be rendered with monospace
// fallback and have a '1ch' measurement much shorter than 25px.
for (let i = 0; i < testCa