test_that("start intervals are NA", {
  x <- tibble::tribble(
    ~chrom, ~start, ~end,
    "chr1", 1, 100,
    "chr1", 150, 200,
    "chr2", 200, 300
  )

  res <- interval_spacing(x)

  first <- res |>
    group_by(chrom) |>
    slice(1) |>
    select(chrom:end)

  nas <- filter(res, is.na(.spacing)) |>
    select(chrom:end)

  expect_true(all(first == nas))
})

# from bedtools2
test_that("bt test succeeds", {
  x <- tibble::tribble(
    ~chrom, ~start, ~end,
    "chr1", 20, 30,
    "chr1", 25, 40,
    "chr1", 40, 50,
    "chr1", 60, 80,
    "chr1", 75, 100,
    "chr1", 105, 110,
    "chr2", 115, 130,
    "chr2", 120, 160,
    "chr2", 170, 180
  )

  res <- interval_spacing(x)

  exp <- c(NA, -5, 0, 10, -5, 5, NA, -10, 10)
  expect_equal(res$.spacing, exp)
})