Feature flag-driven development can increase the speed of delivering value to customers, but it also adds complexity to testing. The article discusses five types of tests that might be part of a testing strategy: unit tests, integration tests, end-to-end tests, QA testing, and user acceptance testing (UAT). Unit tests should remain unchanged when using feature flags. However, integration and end-to-end tests become more complex due to the potential variations in feature flag states. The article suggests several strategies for automated tests, such as testing the current production state and creating testing personas. Additionally, it emphasizes the importance of testing in production, allowing QA and UAT teams to validate functionality in a real environment before exposing it to all users.