test_that("stamp_logo_png preserves image dimensions and returns the path invisibly", {
  p <- tempfile(fileext = ".png")
  on.exit(unlink(p), add = TRUE)
  grDevices::png(p, width = 600, height = 240); plot(1:5); grDevices::dev.off()
  in_dim <- dim(png::readPNG(p))[1:2]

  expect_invisible(out <- stamp_logo_png(p))
  expect_identical(out, p)
  expect_identical(dim(png::readPNG(p))[1:2], in_dim)  # overwritten at same size
})

test_that("stamp_logo_png runs for every type/variant/position combination", {
  p <- tempfile(fileext = ".png")
  on.exit(unlink(p), add = TRUE)
  grDevices::png(p, width = 500, height = 200); plot(1:5); grDevices::dev.off()

  for (ty in c("wordmark", "mark")) {
    for (va in c("light", "dark")) {
      for (pos in c("bottom-right", "bottom-left", "top-right", "top-left")) {
        expect_no_error(stamp_logo_png(p, type = ty, variant = va, position = pos))
      }
    }
  }
})

test_that("stamp_logo_png validates its inputs", {
  expect_error(stamp_logo_png(tempfile(fileext = ".png")))  # file does not exist
  # invalid type is rejected by match.arg() before the file is touched
  expect_error(stamp_logo_png(tempfile(fileext = ".png"), type = "banner"))
})