test_that("proof bundle has stable fields", {
  ref <- stat_reference(10.4, "unemployment rate", "Spain", "2025", "percent", "Eurostat")
  clm <- stat_claim(10.4, "unemployment rate", "Spain", "2025", "%", "Eurostat")
  aud <- audit_stat_ai(ref, clm)
  prf <- proof_bundle(aud)
  expect_s3_class(prf, "stat_proof")
  expect_match(prf$proof_id, "^PCSA:")
  expect_equal(nchar(prf$sha256), 64)
})