How to Test Internationalization (i18n) Before It Breaks in Production

Internationalization bugs often appear when a product adds locales: translated text may overflow, dates and numbers may use the wrong convention, and right-to-left layouts may misalign. String length varies by phrase, so test representative translations rather than assuming a fixed expansion percentage.

AI-assisted changes can introduce hardcoded strings or locale assumptions. The same checks apply to human-written changes: verify the supported locales and the actual rendered output.

Common i18n Bugs to Check

• Hardcoded strings instead of translation keys
• Date/time formatting without locale awareness
• Number formatting (1,000 vs 1.000) not localized
• Text overflow when translated strings are longer
• Currency display hardcoded to $ instead of locale-appropriate symbol
• RTL layout not mirrored for Arabic/Hebrew
• String concatenation that breaks in languages with different word order

Testing i18n Systematically

1. List supported locales and the flows that matter most, such as signup, checkout, and settings. 2. Prepare fixed inputs: a known date and time zone, a currency amount, a long translated label, and mixed left-to-right/right-to-left text. 3. Run each flow in every target locale and viewport. Assert the expected date, number, and currency output, plus visible labels and working controls. 4. Check screenshots for clipping, overlap, and reading order. 5. File a reproducible defect with locale, viewport, input, expected output, and actual output.

Automate representative locale checks on PRs and review changes to translation files or formatting code. TestSprite can help exercise configured flows, but coverage depends on the locales and assertions you provide. Add manual language review for meaning and tone.

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