Because software testing is a repetitive and time-intensive task, a practical solution is to turn to automation. Test automation, however, requires programming skills. Testers, who typically know a lot about the application under test, often do not have the programming skills to automate the testing effort. Grammar-based test generation (GBTG) uses context-free grammars to generate strings in the language described by the grammar. Given a grammar, a GBTG algorithm can produce test cases for the application under test. Since testers typically have little programming skills and are not likely to develop the grammars needed for practical testing, the power of GBTG is unavailable to many testing practitioners. To help address this problem, we have developed Dervish, a graphical user interface which allows testers to use the power of GBTG. Our new tool allows testers to modify parts of a grammar, generate test cases, and visualize generation trees. To demonstrate the benefits of Dervish, we present the results of three case studies.