test_that("gui_datatable returns a DT htmlwidget", {
  df <- data.frame(x = 1:3, y = c("a", "b", "c"))
  widget <- gui_datatable(df)
  expect_s3_class(widget, "datatables")
})

test_that("gui_snapshot_png writes a real PNG file", {
  path <- gui_snapshot_png(plot(1:10, 1:10))
  expect_true(file.exists(path))
  expect_gt(file.size(path), 0)
  expect_match(path, "\\.png$")
  unlink(path)
})

test_that("gui_render_report renders a real HTML file from a populated store", {
  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 <- biocharkit::fit_langmuir(Ce, qe)

  set.seed(1)
  Temp <- seq(25, 800, by = 10)
  Weight <- 100 - 5 * (Temp > 110) - 40 / (1 + exp(-(Temp - 340) / 20)) + rnorm(length(Temp), 0, 0.15)
  tga_curve <- data.frame(temperature_C = Temp, weight_pct = pmax(Weight, 20))
  tga_stages <- biocharkit::tga_stages(tga_curve)
  tga_peaks <- biocharkit::find_dtg_peaks(biocharkit::tga_dtg(tga_curve), min_prominence = 0.05)
  kis <- biocharkit::tga_kinetics_kissinger(c(5, 10, 15, 20), c(320, 335, 344, 351))

  store <- list(
    sample_ids = biocharkit::parse_sbc_id(c("SBC300-15")),
    adsorption = NULL,
    isotherm = list(model = "langmuir", batch = FALSE,
                     params = data.frame(model = "Langmuir", Qmax_mgg = fit$Qmax,
                                          KL_Lmg = fit$KL, R2 = fit$R2), plot_path = NULL),
    kinetics = NULL, thermo = NULL, ftir_functional_groups = NULL,
    ftir_peak_assignment = NULL, xrd = NULL, bet = NULL,
    tga = list(batch = FALSE, stages = tga_stages, peaks = tga_peaks, plot_path = NULL),
    tga_kissinger = data.frame(Ea_kJmol = kis$Ea_kJmol, A_min1 = kis$A_min1, R2 = kis$R2),
    proximate = NULL, ultimate = NULL, correlation = NULL
  )
  out <- tempfile(fileext = ".html")
  gui_render_report(store, out)
  expect_true(file.exists(out))
  expect_gt(file.size(out), 0)
  html <- readLines(out, warn = FALSE)
  expect_true(any(grepl("Isotherm", html)))
  expect_true(any(grepl("TGA Analysis", html)))
  expect_true(any(grepl("Kissinger", html)))
  unlink(out)
})

test_that("gui_render_report handles an entirely empty store gracefully", {
  empty_store <- list(sample_ids = NULL, adsorption = NULL, isotherm = NULL,
                       kinetics = NULL, thermo = NULL, ftir_functional_groups = NULL,
                       ftir_peak_assignment = NULL, xrd = NULL, bet = NULL,
                       tga = NULL, tga_kissinger = NULL,
                       proximate = NULL, ultimate = NULL, correlation = NULL)
  out <- tempfile(fileext = ".html")
  gui_render_report(empty_store, out)
  expect_true(file.exists(out))
  unlink(out)
})