test_that("nrm_response_curve fits quadratic", {
  data(nrm_example, package = "NRMstatsML")
  rc <- nrm_response_curve(nrm_example,
          input_var = "N", response_var = "crop_yield", type = "quadratic")
  expect_s3_class(rc, "nrm_response_curve")
  expect_equal(rc$type, "quadratic")
  expect_true(is.numeric(rc$r_squared))
})

test_that("nrm_response_curve fits linear", {
  data(nrm_example, package = "NRMstatsML")
  rc <- nrm_response_curve(nrm_example,
          input_var = "N", response_var = "crop_yield", type = "linear")
  expect_equal(rc$type, "linear")
  expect_true(is.numeric(rc$r_squared))
})

test_that("nrm_optimize_input works on quadratic curve", {
  data(nrm_example, package = "NRMstatsML")
  rc  <- nrm_response_curve(nrm_example,
           input_var = "N", response_var = "crop_yield", type = "quadratic")
  opt <- nrm_optimize_input(rc, price_ratio = 0.5)
  expect_s3_class(opt, "nrm_optimize_input")
  expect_true(is.numeric(opt$biophysical_optimum))
  expect_equal(opt$price_ratio, 0.5)
})

test_that("nrm_optimize_input errors on wrong class", {
  expect_error(nrm_optimize_input(list()), "class 'nrm_response_curve'")
})

test_that("nrm_response_curve rejects unknown type", {
  data(nrm_example, package = "NRMstatsML")
  expect_error(
    nrm_response_curve(nrm_example, input_var = "N",
                       response_var = "crop_yield", type = "exponential"),
    "should be one of"
  )
})