test_that("identity", {
  f1 <- factor(c("a", "b"))

  expect_identical(fct_relabel(f1, identity), f1)
})

test_that("gives useful errors", {
  f1 <- factor("a")

  expect_snapshot(error = TRUE, {
    fct_relabel(f1, 1)
    fct_relabel(f1, function(x) 1)
    fct_relabel(f1, function(x) x[-1])
  })
})

test_that("total collapse", {
  f1 <- factor(letters)
  new_levels <- function(x) rep("1", length(x))

  expect_identical(fct_relabel(f1, new_levels), factor(new_levels(letters)))
})

test_that("additional arguments", {
  f1 <- factor(letters)

  expect_identical(fct_relabel(f1, paste0, "."), factor(paste0(letters, ".")))
})

test_that("formulas are coerced to functions", {
  f1 <- factor(letters)

  expect_identical(
    fct_relabel(f1, ~ paste0(.x, ".")),
    factor(paste0(letters, "."))
  )
})

test_that("string input is coerced to a factor", {
  expect_identical(
    fct_relabel(LETTERS[1:2], function(x) x),
    factor(LETTERS[1:2])
  )
})