test_that("diff_manifest classifies added, changed and removed", {
  dir <- tempfile(); dir.create(dir)
  f1 <- file.path(dir, "a.out"); writeLines("x", f1)
  m1 <- scan_out(dir, pattern = "\\.out$")
  f2 <- file.path(dir, "b.out"); writeLines("y", f2)
  Sys.sleep(1.1); writeLines("xx", f1)
  m2 <- scan_out(dir, pattern = "\\.out$")
  d <- diff_manifest(m1, m2)
  expect_true(f2 %in% d$added); expect_true(f1 %in% d$changed)
  expect_true(d$any)
  expect_false(diff_manifest(m2, m2)$any)
})