test_that("Minimal s-t separators work", {
  g <- graph_from_literal(a - -1:3 - -5 - -2:4 - -b, 1 - -2, 3 - -4)
  stsep <- min_st_separators(g)
  ims <- sapply(stsep, is_min_separator, graph = g)
  expect_equal(ims, rep(TRUE, 9))
})