test_that("Silverman rule of thumb handles bad inputs", {
  expect_error(bw.rot(c(1:9, NA)), "There are missing values")

  x <- c(1:9, 100)
  expect_lt(bw.rot(x, robust = TRUE), bw.rot(x, robust = FALSE))
})

test_that("Silverman rule of thumb works", {
  x <- 1:32 / 4.69041575982343 # n = 32, n^(-1/5) = 1/2, sd(x) = 2
  expect_equal(bw.rot(x), 1.059223841048812, tolerance = 1e-15)
})