test_that("cluster_fast_greedy works", {
  withr::local_seed(42)

  g <- make_graph("Zachary")
  fc <- cluster_fast_greedy(g)

  expect_that(modularity(g, fc$membership), equals(max(fc$modularity)))
  expect_that(
    as.vector(membership(fc)),
    equals(c(
      1, 3, 3, 3, 1, 1, 1, 3, 2, 3,
      1, 1, 3, 3, 2, 2, 1, 3, 2, 1,
      2, 3, 2, 2, 2, 2, 2, 2, 2, 2,
      2, 2, 2, 2
    ))
  )
  expect_that(length(fc), equals(3))
  expect_that(as.numeric(sizes(fc)), equals(c(8, 17, 9)))

  d <- as.dendrogram(fc)
  expect_that(print(d), prints_text("2 branches.*34 members.*height 33"))
  expect_that(
    print(d[[1]]),
    prints_text("2 branches.*17 members.*height 32")
  )
  expect_that(
    print(d[[2]]),
    prints_text("2 branches.*17 members.*height 30")
  )
  m2 <- cut_at(fc, no = 3)
  expect_that(
    modularity(g, m2),
    equals(fc$modularity[length(fc$modularity) - 2])
  )
})