test_that("multiplication works", {
  expect_equal(round(long_run_covariance(electricity, 0, bartlett_kernel)[2, 3], 4), 262.2927)
  expect_equal(round(long_run_covariance(electricity, 1, bartlett_kernel)[2, 3], 4), 262.2927)
  expect_equal(round(long_run_covariance(electricity, 2, bartlett_kernel)[2, 3], 4), 453.4216)
  expect_equal(round(long_run_covariance(electricity, 2, parzen_kernel)[2, 3], 4), 357.8572)
})
