test_that("safe_unit returns expected output", {
  expect_null(safe_unit(1, NULL))
  expect_null(safe_unit(NULL, "inches"))
  expect_null(safe_unit(NULL, NULL))

  valid_unit <- safe_unit(1, "inches")
  expect_type(valid_unit, "language")
  expect_identical(
    eval(valid_unit),
    grid::unit(1, "inches")
  )
})

test_that("safe_arrow returns expected output", {
  expect_null(safe_arrow(30, NULL))
  expect_null(safe_arrow(NULL, 0.1))
  expect_null(safe_arrow(NULL, NULL))

  valid_arrow <- safe_arrow(30, 0.1)
  expect_type(valid_arrow, "language")
  expect_identical(
    eval(valid_arrow),
    arrow(
      angle = 30,
      length = unit(0.1, "inches"),
      "last",
      "closed"
    )
  )
})