test_that("plot_isotherm runs without error for all 5 models", {
  Ce <- c(2, 5, 10, 20, 35, 50, 70, 90)
  qe <- c(0.8, 1.6, 2.3, 3.0, 3.6, 4.0, 4.4, 4.6)
  pdf(NULL)
  on.exit(dev.off())

  expect_no_error(plot_isotherm(fit_langmuir(Ce, qe), Ce, qe, model = "langmuir"))
  expect_no_error(plot_isotherm(fit_freundlich(Ce, qe), Ce, qe, model = "freundlich"))
  expect_no_error(plot_isotherm(fit_temkin(Ce, qe), Ce, qe, model = "temkin"))
  expect_no_error(plot_isotherm(fit_dr(Ce, qe), Ce, qe, model = "dr"))
  expect_no_error(plot_isotherm(fit_sips(Ce, qe), Ce, qe, model = "sips"))
})

test_that("plot_isotherm infers langmuir/freundlich when model is omitted", {
  Ce <- c(2, 5, 10, 20, 35, 50, 70)
  qe <- c(0.8, 1.6, 2.3, 3.0, 3.6, 4.0, 4.4)
  pdf(NULL)
  on.exit(dev.off())
  expect_no_error(plot_isotherm(fit_langmuir(Ce, qe), Ce, qe))
  expect_no_error(plot_isotherm(fit_freundlich(Ce, qe), Ce, qe))
})

test_that("plot_kinetics runs without error for all 4 models", {
  t <- c(5, 15, 30, 60, 120, 240)
  qt <- c(1.2, 2.1, 2.9, 3.6, 4.0, 4.2)
  pdf(NULL)
  on.exit(dev.off())

  expect_no_error(plot_kinetics(fit_pfo(t, qt), t, qt, model = "pfo"))
  expect_no_error(plot_kinetics(fit_pso(t, qt), t, qt, model = "pso"))
  expect_no_error(plot_kinetics(fit_elovich(t, qt), t, qt, model = "elovich"))
  expect_no_error(plot_kinetics(fit_intraparticle(t, qt), t, qt, model = "intraparticle"))
})

test_that("plot_ftir_spectrum runs without error", {
  spec <- data.frame(wavenumber_cm1 = seq(4000, 400, by = -10),
                      intensity = runif(361, 0, 1))
  pdf(NULL)
  on.exit(dev.off())
  expect_no_error(plot_ftir_spectrum(spec))
})

test_that("save_tiff produces a real file", {
  Ce <- c(2, 5, 10, 20, 35, 50, 70)
  qe <- c(0.8, 1.6, 2.3, 3.0, 3.6, 4.0, 4.4)
  fit <- fit_langmuir(Ce, qe)
  path <- tempfile(fileext = ".tif")
  save_tiff(plot_isotherm(fit, Ce, qe), filename = path)
  expect_true(file.exists(path))
  expect_gt(file.size(path), 0)
  unlink(path)
})