if (require("testthat") && require("sjmisc")) {
  data(efc)
  efc$ID <- sample(1:4, nrow(efc), replace = TRUE) # fake-ID



  test_that("de_mean", {
    de_mean(efc, c12hour, barthtot, grp = ID)
    de_mean(efc, c12hour, barthtot, grp = ID, append = FALSE)
    de_mean(efc, c12hour, barthtot, grp = ID, append = FALSE, suffix.dm = "dm", suffix.gm = "gm")
    de_mean(efc, c12hour, barthtot, grp = ID, suffix.dm = "dm", suffix.gm = "gm")
    de_mean(efc, c12hour, barthtot, grp = "ID")
  })
}