Run transformations on all *-in.R files in a test directory and compare them with their *-out.R counterpart.

  sub_test = NULL,
  dry = "off",
  write_tree = NA,



The test to run. It corresponds to a folder name in tests/testthat.


A regex pattern to further reduce the amount of test files to be tested in the test. sub_test must match the beginning of file names in tests/testthat. NULL matches all files.


To indicate whether styler should run in dry mode, i.e. refrain from writing back to files ."on" and "fail" both don't write back, the latter returns an error if the input code is not identical to the result of styling. "off", the default, writes back if the input and output of styling are not identical.


Whether or not the tree structure of the test should be computed and written to a file. Note that this needs R >= 3.2 (see set_arg_write_tree()). If the argument is set to NA, the function determines whether R >= 3.2 is in use and if so, trees will be written.


A function to apply to the content of in_item.


Parameters passed to transformer function.


Each file name that matches test and sub_test and ends with "-in.R" is considered as an input to test. Its counterpart, the reference to compare it against is the *-out.R file. It is constructed by taking the substring of the *-in.R file before the last dash and adding -out.R. In contrast to older versions of this function, every *-out.R file has just one in file.