test_that("gp_opts returns correct default values", {
  gp <- gp_opts()
  expect_equal(gp$basis_prop, 0.2)
  expect_equal(gp$boundary_scale, 1.5)
  expect_equal(gp$ls_mean, 21)
  expect_equal(gp$ls_sd, 7)
  expect_equal(gp$ls_min, 0)
  expect_equal(gp$ls_max, 60)
  expect_equal(gp$alpha_sd, 0.01)
  expect_equal(gp$kernel, "matern")
  expect_equal(gp$matern_order, 3 / 2)
  expect_equal(gp$w0, 1.0)
})

test_that("gp_opts sets matern_order to Inf for squared exponential kernel", {
  gp <- gp_opts(kernel = "se")
  expect_equal(gp$matern_order, Inf)
})

test_that("gp_opts sets matern_order to 1/2 for Ornstein-Uhlenbeck kernel", {
  gp <- gp_opts(kernel = "ou")
  expect_equal(gp$matern_order, 1 / 2)
})

test_that("gp_opts warns for uncommon Matern kernel orders", {
  expect_warning(gp_opts(matern_order = 2), "Uncommon Matern kernel order")
})

test_that("gp_opts handles deprecated matern_type parameter", {
  lifecycle::expect_deprecated(gp_opts(matern_type = 5 / 2))
  gp <- suppressWarnings(gp_opts(matern_type = 5 / 2))
  expect_equal(gp$matern_order, 5 / 2)
})

test_that("gp_opts stops for incompatible matern_order and matern_type", {
  expect_error(
    suppressWarnings(gp_opts(matern_order = 3 / 2, matern_type = 5 / 2)),
    "must be the same, if both are supplied."
  )
})

test_that("gp_opts warns about uncommon Matern kernel orders", {
  expect_warning(gp_opts(matern_order = 2), "Uncommon Matern kernel order")
})