x1 <- c("1", "2", "1", "1")
x2 <- c("11", "21", "12", "11")
x3 <- c("111", "211", "121", "112")

test_that("factors do nothing", {
  agg1 <- aggregation_structure(list(x1, x2, x3), 1:4)
  f <- factor(x2, levels = c("11", "21", "12"))
  agg2 <- aggregation_structure(list(x1, f, x3), 1:4)
  expect_identical(agg1, agg2)

  f <- factor(x2, levels = c("11", "21", "12", "99"))
  expect_identical(agg2, aggregation_structure(list(x1, f, x3), 1:4))

  f <- factor(replace(x2, 2, NA), levels = c("11", "21", "12"))
  expect_error(aggregation_structure(list(x1, addNA(f), x3), 1:4))
})

test_that("order is preserved", {
  agg <- aggregation_structure(list(x1, x2, x3))
  expect_identical(unlist(levels(agg)), unique(c(x1, x2, x3)))
  
  ord <- c(2, 4, 1, 3)
  agg <- aggregation_structure(list(x1[ord], x2[ord], x3[ord]))
  expect_identical(unlist(levels(agg)), unique(c(x1[ord], x2[ord], x3[ord])))
})

test_that("errors work", {
  expect_error(aggregation_structure(list()))
  expect_error(aggregation_structure(list(x1, x2, x3), 1:3))
  expect_error(aggregation_structure(list(x1, x2, x3, x3)))
  expect_error(aggregation_structure(list(x1, x2)))
  expect_error(aggregation_structure(list(1:2, c(11, NA))))
  expect_error(aggregation_structure(list(1:2, c(11, 11, 12))))
  expect_error(aggregation_structure(list(1:2, c(3, 3), c(4, 5))))
  expect_error(aggregation_structure(list(1:2, c(3, 3), c(4, ""))))
})