[JOSS Review] Add helper-data.R to tests/testthat

[fawda123]

There are several objects that are duplicated across test files. You can define global objects used in each test file by adding them to helper-data.R. For example, this code is repeated in a lot of the files:

copy_lsn_to_temp()
temp_path <- paste0(tempdir(), "/MiddleFork04.ssn")
mf04p <- ssn_import(
    temp_path,
    predpts = c("pred1km", "CapeHorn", "Knapp"),
    overwrite = TRUE
  )

Adding it to helper-data.R ensures it's only created once and will reduce the time needed when the tests are run. You can also load any packages in this file that are used in more than one test file.

openjournals/joss-reviews#6389

[michaeldumelle]

Thanks @fawda123; this is a great suggestion that will be so helpful in my other software packages too! Incorporated in this commit (on the develop branch).