test_that("ild_as_tsibble round-trips key and index", {
  skip_if_not_installed("tsibble")
  d <- ild_simulate(n_id = 4, n_obs_per = 5, seed = 11)
  x <- ild_prepare(d, id = "id", time = "time")
  ts <- ild_as_tsibble(x)
  expect_true(inherits(ts, "tbl_ts"))
  expect_equal(tsibble::key_vars(ts), "id")
  expect_equal(tsibble::index_var(ts), "time")
})

test_that("ild_prepare infers id and time from tbl_ts", {
  skip_if_not_installed("tsibble")
  d <- ild_simulate(n_id = 3, n_obs_per = 4, seed = 12)
  x0 <- ild_prepare(d, id = "id", time = "time")
  ts <- ild_as_tsibble(x0)
  x1 <- ild_prepare(ts)
  expect_true(is_ild(x1))
  expect_equal(attr(x1, "ild_id", exact = TRUE), "id")
  expect_equal(attr(x1, "ild_time", exact = TRUE), "time")
  expect_equal(nrow(x0), nrow(x1))
})