When implementing a Data-Driven Testing Framework, what is a common data source used for test inputs?

In a Data-Driven Testing Framework, Excel files are a common data source for test inputs. Test data is often stored in spreadsheets, allowing testers to easily manage, update, and manipulate test data. Excel files provide a structured format for organizing different sets of test data, making it convenient to perform data-driven testing and execute test cases with multiple input variations.