test_that("nrm_data_check passes valid data", {
  data(nrm_example, package = "NRMstatsML")
  expect_invisible(nrm_data_check(nrm_example, verbose = FALSE))
})

test_that("nrm_data_check errors on non-data-frame", {
  expect_error(nrm_data_check(list(a = 1)), "`data` must be a data frame")
})

test_that("nrm_mann_kendall returns correct structure", {
  data(nrm_example, package = "NRMstatsML")
  mk <- nrm_mann_kendall(nrm_example, time_var = "year",
                          value_var = "crop_yield")
  expect_s3_class(mk, "nrm_mann_kendall")
  expect_true(is.numeric(mk$tau))
  expect_true(is.numeric(mk$p_value))
  expect_true(mk$p_value >= 0 && mk$p_value <= 1)
  expect_true(mk$trend_direction %in%
                c("increasing", "decreasing", "no trend"))
})

test_that("nrm_sens_slope returns slope and CI", {
  data(nrm_example, package = "NRMstatsML")
  ss <- nrm_sens_slope(nrm_example, time_var = "year",
                        value_var = "crop_yield")
  expect_s3_class(ss, "nrm_sens_slope")
  expect_true(is.numeric(ss$slope))
  expect_length(ss$conf_int, 2)
  expect_true(ss$conf_int[1] <= ss$conf_int[2])
})

test_that("nrm_structural_break returns n_breaks", {
  data(nrm_example, package = "NRMstatsML")
  sb <- nrm_structural_break(nrm_example, time_var = "year",
                               value_var = "crop_yield")
  expect_s3_class(sb, "nrm_structural_break")
  expect_true(is.numeric(sb$n_breaks))
  expect_true(sb$n_breaks >= 0)
})

test_that("nrm_trend integrates all sub-tests", {
  data(nrm_example, package = "NRMstatsML")
  tr <- nrm_trend(nrm_example, time_var = "year",
                   value_var = "crop_yield", breaks = TRUE)
  expect_s3_class(tr, "nrm_trend")
  expect_named(tr, c("mann_kendall", "sens_slope", "structural_breaks",
                      "data", "time_var", "value_var", "call"))
  expect_false(is.null(tr$structural_breaks))
})

test_that("nrm_trend with breaks = FALSE has NULL structural_breaks", {
  data(nrm_example, package = "NRMstatsML")
  tr <- nrm_trend(nrm_example, time_var = "year",
                   value_var = "soil_OC", breaks = FALSE)
  expect_null(tr$structural_breaks)
})

test_that("nrm_mann_kendall errors on missing column", {
  data(nrm_example, package = "NRMstatsML")
  expect_error(nrm_mann_kendall(nrm_example, time_var = "year",
                                 value_var = "nonexistent"),
               "Column\\(s\\) not found")
})