test_that("gregorian", {
  expect_equal(gregorian_date(2025, 1, 1), as_gregorian("2025-01-01"))
  expect_equal(as.Date(gregorian_date(2025, 4, 19)), as.Date("2025-04-19"))
  expect_error(gregorian_date(2025, 13, 1))
  expect_error(gregorian_date(2025, 2, 30))
  expect_error(gregorian_date(2025, 2, 29))
  expect_error(gregorian_date(2024.4, 2, 12))
  expect_no_error(gregorian_date(2025, 2, 28))
  expect_no_error(gregorian_date(2020, 2, 29))
  expect_no_error(gregorian_date(2000, 2, 29))
  expect_error(gregorian_date(1900, 2, 29))
  expect_no_error(gregorian_date(NA, 2, 29))
  expect_error(gregorian_date(NA, 2, 30))
  expect_no_error(gregorian_date(NA, NA, 31))
  expect_error(gregorian_date(NA, NA, 32))
  expect_no_error(gregorian_date(NA, NA, NA))
  expect_error(gregorian_date(1:3, 2:4, 5:6))
  expect_no_error(gregorian_date(1:3, 2:4, 5))
  expect_equal(
    gregorian_date(1967, 5, 2) |>
      cal_gregorian$from_rd() |>
      cal_gregorian$to_rd(),
    gregorian_date(1967, 5, 2) |> as.numeric()
  )
})

test_that("parts_of_date", {
  yr2025 <- gregorian_date(2025, 1, 1) + (0:364)
  expect_equal(day_of_week(yr2025)[1], "Wednesday")
  expect_equal(
    day_of_month(yr2025),
    c(1:31, 1:28, 1:31, 1:30, 1:31, 1:30, 1:31, 1:31, 1:30, 1:31, 1:30, 1:31)
  )
  expect_equal(day_of_year(yr2025), 1:365)
  expect_equal(days_remaining(yr2025), 364:0)
  expect_equal(
    month_of_year(yr2025),
    c(
      rep(1, 31),
      rep(2, 28),
      rep(3, 31),
      rep(4, 30),
      rep(5, 31),
      rep(6, 30),
      rep(7, 31),
      rep(8, 31),
      rep(9, 30),
      rep(10, 31),
      rep(11, 30),
      rep(12, 31)
    )
  )
  expect_equal(week_of_month(yr2025)[1:31], week_of_year(yr2025)[1:31])
  expect_equal(
    week_of_year(yr2025),
    c(rep(1, 5), rep(2:52, rep(7, 51)), rep(1, 3))
  )
  expect_true(all(day_of_year(yr2025) + days_remaining(yr2025) == 365))
  expect_no_error(as_gregorian(1:1e5) |> as.list() |> validate_gregorian())
})