Unit testing is essential in software development to ensure code functionality and prevent the introduction of bugs. However, challenges such as time constraints and insufficient resource allocation often impede comprehensive testing efforts, leaving software systems vulnerable to regression. To address this issue, we introduce Modest, a language-agnostic approach to unit test generation that uses metamodels and execution traces. This method ensures non-regression by replaying scenarios captured from real-world executions. We demonstrate the application of Modest to Pharo codebases by generating unit tests for two projects.