Localization Testing and QA Workflow

The workflow in six gates

1. 1. Static checks

   Reject hardcoded UI strings, invalid locale tags, missing keys, placeholder mismatches, and unsafe concatenation in continuous integration.

2. 2. Pseudolocalization

   Transform source messages to expose clipping, fixed widths, untranslated strings, token corruption, and bidirectional assumptions before translation.

3. 3. Locale automation

   Run number, currency, date, timezone, plural, address, and phone fixtures with explicit locales and timezones.

4. 4. Visual regression

   Capture representative long-text, CJK, combining-mark, emoji, and RTL screens at phone, tablet, desktop, and 200% zoom.

5. 5. Linguistic QA

   Have qualified native-language reviewers assess meaning, terminology, tone, grammar, cultural suitability, and functional context.

6. 6. Regional validation

   Test real device language, region, timezone, keyboard, calendar, numbering system, and currency combinations before release.

A pseudolocalization transform that finds real bugs

A useful pseudo locale keeps messages readable while expanding text, replacing letters with accented variants, preserving interpolation tokens, and surrounding output with unmistakable markers. Use a separate mirrored RTL pseudo locale; simply reversing a whole string does not model the Unicode bidirectional algorithm.

const accentMap: Record<string, string> = {
  a: "à", e: "ë", i: "ï", o: "ô", u: "ü",
  A: "Å", E: "Ë", I: "Ï", O: "Ö", U: "Û",
};

export function pseudo(message: string): string {
  const tokens: string[] = [];
  const protectedMessage = message.replace(/{[^}]+}|%w|<[^>]+>/g, (token) => {
    tokens.push(token);
    return "__TOKEN_" + (tokens.length - 1) + "__";
  });

  const accented = [...protectedMessage]
    .map((char) => accentMap[char] ?? char)
    .join("");
  const expanded = accented + " " + "~".repeat(Math.ceil(message.length * 0.35));

  return "⟦" + expanded.replace(/__TOKEN_(d+)__/g, (_, index) => tokens[Number(index)]) + "⟧";
}

• Fail if any source-language message appears unchanged outside an allowlist.
• Verify placeholders, HTML tags, ICU plural branches, and line breaks survive the transformation.
• Include a long expansion locale and an RTL mirrored locale in every pull-request preview.

Locale test matrix

Choose representative stress locales

Browser and device simulation

1. Change the operating-system language and region independently; restart the app where the platform requires it.
2. Set a timezone that crosses the tested date boundary and include a daylight-saving transition.
3. Install and use a regional keyboard or input method editor, then test typing, composition, selection, and paste.
4. Request an alternate numbering system through a Unicode locale extension such as `ar-EG-u-nu-latn`.
5. Test narrow phone widths, landscape, desktop, browser text zoom, and 200% page zoom.
6. Inspect logical navigation order, focus visibility, screen-reader labels, and whether RTL changes meaningfully directional icons.

Automate stable contracts

Set locale and timezone explicitly in tests. Prefer semantic assertions over machine-default output and keep screenshots on a pinned browser/runtime.

import test from "node:test";
import assert from "node:assert/strict";

test("JPY uses its runtime currency precision", () => {
  const formatter = new Intl.NumberFormat("ja-JP", {
    style: "currency", currency: "JPY",
  });
  assert.equal(formatter.resolvedOptions().maximumFractionDigits, 0);
});

test("pseudo keeps the interpolation token", () => {
  const output = pseudo("Welcome, {name}");
  assert.match(output, /{name}/);
  assert.match(output, /^⟦/);
});

Copyable release gate