Localization testing

Localization testing is the process of verifying that the localized version of a software application or website works properly for a specific language, region, and culture. This goes beyond checking translation accuracy to include testing the user interface, date and time formats, currency display, cultural appropriateness, and functional behavior. The goal is to catch issues that could break the user experience or make the product feel foreign or inappropriate to the target audience before it reaches real users.

➡️ Types of localization testing #️⃣

1. Pseudo-localization

Pseudo-localization replaces the source text with modified versions that simulate translation without actually translating. For example, “Account Settings” becomes “[!!! Àççôûñţ Šéţţîñĝš !!!]”. This tests internationalization readiness before real translation begins.

2. Bidi testing

Bidirectional (bidi) testing verifies that right-to-left (RTL) languages like Arabic and Hebrew display correctly, with proper text direction, UI mirroring, and mixed-direction content handling.

3. Overflow testing

Testing whether translated text fits within UI constraints, since many languages expand significantly compared to English (German and Dutch can expand 35% or more; French and Spanish, 15-30%).

4. Placeholder testing

Verifying that variables, parameters, and format specifiers (like {username}, %s, or {{date}}) are preserved correctly in translations and display properly when replaced with actual data.

5. Pluralization testing

Testing that the application handles plural forms correctly across languages, since different languages have different pluralization rules (English has 2 forms, Arabic has 6, and Polish has 3).

6. Layout validation

Checking that UI elements, graphics, spacing, and overall design work correctly with translated content and maintain visual hierarchy and usability.

7. Date and currency testing

Verifying that dates, times, numbers, and currencies display in the correct format for each locale (DD/MM/YYYY vs MM/DD/YYYY, commas vs periods in numbers, currency symbols).

8. Font rendering

Testing that fonts display correctly for all characters in the target language, including special characters, diacritics, and non-Latin scripts.

9. A/B testing

Running experiments with different localization approaches to measure which translations, cultural adaptations, or UI variations perform better with target audiences.

10. Character encoding

Testing that text is stored, transmitted, and displayed using the correct character encoding (UTF-8) to prevent garbled text or data corruption.

☝️ Best practices for localization testing #️⃣

• Test early and often throughout development, not just before release.
• Use native speakers or professional testers from the target market for cultural validation.
• Automate what you can (encoding checks, placeholder validation, format verification) but keep manual review for linguistic and cultural appropriateness.
• Test on actual devices and operating systems used in target markets, not just emulators.
• Create a comprehensive test matrix covering all language-specific features.
• Document known limitations and locale-specific behaviors.
• Include localization testing in your CI/CD pipeline.
• Test with real data in the target language, not just sample strings.
• Verify that hotkeys, shortcuts, and keyboard layouts work for each locale.
• Check that help documentation, error messages, and legal text are properly localized.

🛠️ Tools and automations #️⃣

1. Pseudo-localization tools: Android’s built-in pseudolocales, Microsoft’s Multilingual App Toolkit, OneSky.
2. RTL testing: Browser developer tools with dir=“rtl”, Bidi Checker, native device testing.
3. Automated testing frameworks: Selenium, Appium, testRigor (supports multiple test types in one tool).
4. Localization platforms with testing: Localazy, Smartling, Crowdin (many include built-in QA checks).
5. Visual regression testing: Percy, Applitools, BackstopJS.
6. Character encoding validators: W3C Validator, browser encoding inspection tools.