Automated unit test generation using genthat

Your package has examples and vignettes of its overall functionality but no unit tests for individual functions. Writing those is no fun. Yet, when something goes wrong, unit tests are your best tool to quickly pinpoint errors. The genthat package can generate unit tests for you in the popular testthat format. Moreover, it can also be used to create reproductions when you find a bug in someone else’s code. There, instead of generating passing test cases it will generate the smallest, purposefully failing, one.Genthat does not magically create new tests out of the blue, instead it simply extracts the smallest possible test fragments from existing code. It does that by recording the input arguments and return values of all function called by clients of your package. The generated tests concentrate on single functions and test them independently of each other. Therefore a failing test usually locates the error more precisely that a failing chunk of application code. Trying it out on random set of 1500 CRAN packages, genthat managed to reproduce 80% of all function calls, increasing the unit test coverage from 19% to 54%. In this talk we present genthat and discuss testing R code.