epr1 <- with(
  ms_prices,
  elemental_index(price_relative(price, period, product),
                  period, business, contrib = TRUE, na.rm = TRUE)
)

epr2 <- with(
  ms_prices,
  elemental_index(price_relative(price, period, product),
                  period, business, na.rm = TRUE)
)

pias <- with(
  ms_weights,
  aggregation_structure(
    c(expand_classification(classification), list(business)), weight
  )
)

index1 <- aggregate(epr1, pias, na.rm = TRUE)
index2 <- aggregate(epr2, pias, na.rm = TRUE)

test_that("chain is the same as apply", {
  expect_equal(as.matrix(chain(epr1)),
               t(apply(as.matrix(epr1), 1, cumprod)))
  expect_equal(as.matrix(chain(index1)),
               t(apply(as.matrix(index1), 1, cumprod)))
})

test_that("unchain and chain are inverses with no NAs", {
  expect_equal(unchain(chain(index2)), index2)
  expect_failure(expect_equal(unchain(chain(epr2)), epr2))
})

test_that("unchaining/rebasing a chainable index does nothing", {
  expect_equal(unchain(epr1), epr1)
  expect_equal(unchain(index1), index1)
  expect_equal(rebase(epr1), epr1)
  expect_equal(rebase(index1), index1)
})

test_that("chaining a fixed-base index does nothing", {
  expect_equal(chain(epr1), chain(chain(epr1)))
  expect_equal(chain(index1), chain(chain(index1)))
})

test_that("rebase should be the same as division", {
  expect_equal(as.matrix(rebase(chain(epr2), 1:4)),
               as.matrix(chain(epr2)) / 1:4)
  expect_equal(as.matrix(rebase(chain(index2), 1:8)),
               as.matrix(chain(index2)) / 1:8)
})

test_that("chaining returns the correct type of index", {
  expect_true(is_chainable_index(epr1))
  expect_true(is_chainable_index(unchain(chain(epr1))))
  expect_true(is_direct_index(chain(epr1)))
  expect_true(is_chainable_index(index1))
  expect_true(is_chainable_index(unchain(chain(index1))))
  expect_true(is_direct_index(chain(index1)))
  expect_true(is_aggregate_index(chain(index1)))
  expect_true(is_aggregate_index(unchain(chain(index1))))
})

test_that("chaining keeps EA names", {
  expect_equal(as.matrix(chain(as_index(matrix(1:5, 1)))),
               matrix(cumprod(1:5), 1, dimnames = list(1, 1:5)))
})