test_that("scenarios compute changes and detect rebound", {
  sc <- data.frame(scenario = c("drip", "drip+exp", "solar"),
                   crop = c("sugarcane", "sugarcane", NA),
                   water_change = c(-0.3, -0.3, 0),
                   area_change = c(0, 0.8, 0), renewable = c(NA, NA, 1))
  ns <- nexus_scenarios(district_nexus, sc, grid_factor = 1)
  d <- district_nexus
  expect_equal(ns$change$water[ns$change$scenario == "drip"],
               -0.3 * 2000 * 20000)
  expect_false(ns$rebound[["drip"]])
  expect_true(ns$rebound[["drip+exp"]])
  expect_equal(ns$summary$emissions_t[ns$summary$scenario == "solar"], 0)
  expect_equal(ns$summary$emissions_t[1], sum(d$area * d$energy) / 1000)
  expect_output(print(ns), "Rebound")
  expect_error(nexus_scenarios(district_nexus,
                               data.frame(scenario = "x", crop = "kiwi")))
})

test_that("LP matches a known solution and shadow prices", {
  # max 3x + 5y s.t. x <= 4, 2y <= 12, 3x + 2y <= 18 (classic example)
  d <- data.frame(crop = c("x", "y"), yield = c(3, 5), price = 1, cost = 0,
                  water = c(0, 2), energy = c(3, 2))
  na <- nexus_allocation(d, land = Inf, water_limit = 12, energy_limit = 18,
                         extra = list(xcap = list(use = c(1, 0), limit = 4)))
  expect_equal(na$plan$optimal_area, c(2, 6))
  expect_equal(na$objective[["optimal"]], 36)
  sp <- setNames(na$resources$shadow_price, na$resources$resource)
  expect_equal(sp[["water"]], 1.5)
  expect_equal(sp[["energy"]], 1)
  expect_equal(sp[["xcap"]], 0)
})

test_that("allocation respects bounds and limits", {
  na <- nexus_allocation(district_nexus, land = 10000, water_limit = 6e7,
                         energy_limit = 1.2e7)
  x <- na$plan$optimal_area
  d <- district_nexus
  expect_true(all(x >= d$min_area - 1e-6 & x <= d$max_area + 1e-6))
  r <- na$resources
  expect_true(all(r$use <= r$limit + 1e-6))
  # relaxing a binding constraint by one unit raises the objective by its
  # shadow price
  na2 <- nexus_allocation(district_nexus, land = 10000, water_limit = 6e7 + 1,
                          energy_limit = 1.2e7)
  expect_equal(na2$objective[["optimal"]] - na$objective[["optimal"]],
               r$shadow_price[r$resource == "water"], tolerance = 1e-4)
  fo <- nexus_allocation(district_nexus, land = 10000, objective = "food")
  expect_gt(fo$objective[["optimal"]], 0)
  expect_error(nexus_allocation(district_nexus, land = 100))
  expect_output(print(na), "Resources")
})

test_that("trade-off classification works", {
  set.seed(1)
  x <- rnorm(30)
  d <- data.frame(a = x, b = x + rnorm(30, 0, 0.1), c = -x + rnorm(30, 0, 0.1),
                  z = rnorm(30))
  t <- nexus_tradeoffs(d, c("a", "b", "c", "z"), c(TRUE, TRUE, TRUE, TRUE))
  rel <- setNames(t$pairs$relation, paste(t$pairs$indicator_1,
                                          t$pairs$indicator_2))
  expect_equal(rel[["a b"]], "synergy")
  expect_equal(rel[["a c"]], "trade-off")
  t2 <- nexus_tradeoffs(d, c("a", "c"), c(TRUE, FALSE))
  expect_equal(t2$pairs$relation, "synergy")
  expect_error(nexus_tradeoffs(d, "a", TRUE))
  expect_output(print(t), "synergy")
})