Software testing is an important area in the Software Engineering domain, yet it faces significant gaps within Computer Science education. In that context, there is an even less addressed topic: internationalization (i18n) and localization (l10n) tests, which are essential for ensuring software quality in global markets, supporting multiple languages. A key challenge for both large and small companies is the onboarding of new testers without adequate skills, often resulting in insufficient real-world preparation. This paper proposes a tool-assisted training approach designed to enhance the proficiency of l10n and i18n testers through practical, hands-on exercises using real-world failure examples. The effectiveness of our approach was evaluated from two complementary perspectives: i) To assess the effectiveness of the training approach, a case study was conducted within a software industry training setting, comparing novice testers trained with our tool against those receiving conventional training. Results indicated a 150% improvement in bug identification and resolution for testers using the tool, underscoring its effectiveness in enhancing testing skills and overall software quality. ii) To evaluate the perceived usability of the tool developed to support the training activities, a System Usability Scale (SUS) questionnaire was given to five technical leaders responsible for training novice testers. The tool achieved a score of 94.5, positioning its usability between “excellent” and “best imaginable”. This paper highlights the tool’s design, deployment context, and its potential for adoption by other practitioners, aiming to address the current gaps in i18n and l10n tester training, being a promising approach to be used in Software Engineering education.