Building a unit test suite to ensure that functions work as you intend

Most programmers test code obsessively and the practice of unit testing has arisen so that we have a formal way of testing functions that can be automated and help to reduce the time it takes to build even moderately complex code projects. A well-engineered and maintained software package has a unit test suite for as many of its component functions as it is possible to do. In this recipe, we'll look at how to use the usethis package to add the component files and folders for an automated test suite that uses the testthat package. It's beyond the scope of this book to look at the philosophy of why and how to write tests in any detail, but you can check out the testthat package documentation here, https://testthat.r-lib.org/, for a nice primer.

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