test_that("ISO base media is diagnosed before decoding low-ratio binary bytes", {
  prefix <- as.raw(c(0, 0, 0, 32, 102, 116, 121, 112, 105, 115, 111, 109,
    0, 0, 2, 0, 105, 115, 111, 109, 105, 115, 111, 50,
    97, 118, 99, 49, 109, 112, 52, 49))
  bytes <- c(prefix, as.raw(rep(255, 8192)))
  path <- tempfile(fileext = ".txt")
  on.exit(unlink(path), add = TRUE)
  writeBin(bytes, path)
  ratios <- appusage_byte_ratios(bytes)
  expect_lt(ratios$nul_byte_ratio, 0.01)
  expect_lt(ratios$control_byte_ratio, 0.20)
  expect_error(rawToChar(bytes), "embedded nul")
  result <- appusage_source_preflight(path)
  expect_identical(result$status, "binary_signature")
  expect_identical(result$failure_family, "source_binary")
  expect_identical(result$binary_signature, "iso_base_media")
  expect_identical(result$lines, character())
  expect_equal(result$nul_byte_ratio, ratios$nul_byte_ratio)
  expect_equal(result$control_byte_ratio, ratios$control_byte_ratio)
  expect_identical(detect_appusage_type(path), "unknown")
  output <- tempfile("appusage-media-preflight-")
  on.exit(unlink(output, recursive = TRUE), add = TRUE)
  summary <- read_appusage_batch(path, ids = "media", output_dir = output,
    project_name = "Synthetic", project_id = "media", progress = FALSE)
  expect_identical(summary$status, "error")
  expect_identical(summary$failure_family, "source_binary")
  expect_identical(summary$preflight_status, "binary_signature")
  expect_identical(summary$binary_signature, "iso_base_media")
  expect_equal(summary$retry_attempt, 0L)
  expect_true(is.na(summary$data_file))
  expect_true(file.exists(summary$metadata_file))
  metadata <- jsonlite::read_json(summary$metadata_file, simplifyVector = TRUE)
  expect_identical(metadata$source$preflight$binary_signature, "iso_base_media")
  expect_identical(metadata$source$preflight$failure_family, "source_binary")
})

test_that("ftyp text and incomplete box claims do not create media signatures", {
  expect_true(is.na(appusage_binary_signature(charToRaw("ordinary ftyp text"))))
  expect_true(is.na(appusage_binary_signature(charToRaw("2024ftyp ordinary text"))))
  expect_true(is.na(appusage_binary_signature(raw())))
  expect_true(is.na(appusage_binary_signature(charToRaw("ftyp"))))
  expect_true(is.na(appusage_binary_signature(c(as.raw(c(0,0,0,8)), charToRaw("ftyp")))))
  expect_true(is.na(appusage_binary_signature(c(as.raw(c(0,0,0,32)), charToRaw("ftypisom")))))
  path <- tempfile(fileext = ".txt")
  on.exit(unlink(path), add = TRUE)
  writeLines("2024ftyp ordinary text", path)
  result <- appusage_source_preflight(path)
  expect_identical(result$status, "unknown_content")
  expect_identical(result$failure_family, "source_unknown_content")
})