diff --git a/R/topology.R b/R/topology.R
index 917acb6180..a166925b0c 100644
--- a/R/topology.R
+++ b/R/topology.R
@@ -239,10 +239,10 @@ graph.subisomorphic.lad <- function(pattern, target, domains = NULL,
   all.maps <- as.logical(all.maps)
   if (!is.null(domains)) {
     if (!is.list(domains)) {
-      stop("`domains' must be a list of vertex vectors from `target'")
+      cli::cli_abort("{.arg domains} must be a list of vertex vectors from {.arg target}.")
     }
     if (length(domains) != vcount(pattern)) {
-      stop("`domains' length and `pattern' number of vertices must match")
+      cli::cli_abort("{.arg domains} length and {.arg pattern} number of vertices must match.")
     }
     domains <- lapply(domains, function(x) as_igraph_vs(target, x) - 1)
   }
diff --git a/tests/testthat/_snaps/bug-501-rectangles/rectangle-edges.svg b/tests/testthat/_snaps/plot/rectangle-edges.svg
similarity index 100%
rename from tests/testthat/_snaps/bug-501-rectangles/rectangle-edges.svg
rename to tests/testthat/_snaps/plot/rectangle-edges.svg
diff --git a/tests/testthat/test-bug-1032819.R b/tests/testthat/test-bug-1032819.R
deleted file mode 100644
index 04c8548f82..0000000000
--- a/tests/testthat/test-bug-1032819.R
+++ /dev/null
@@ -1,8 +0,0 @@
-test_that("VF2 isomorphism considers colors", {
-  g <- make_full_graph(3)
-  path <- make_ring(3, circular = F)
-  V(g)$color <- c(1, 1, 2)
-  V(path)$color <- c(1, 2, 1)
-  n <- count_subgraph_isomorphisms(path, g, method = "vf2")
-  expect_equal(n, 2)
-})
diff --git a/tests/testthat/test-bug-154.R b/tests/testthat/test-bug-154.R
deleted file mode 100644
index b8deee4032..0000000000
--- a/tests/testthat/test-bug-154.R
+++ /dev/null
@@ -1,6 +0,0 @@
-test_that("graph.get.subisomorphisms.vf2() works even if the graph has a vertex attribute named x", {
-  g <- make_full_graph(4)
-  V(g)$x <- 1:4
-  subs <- graph.get.subisomorphisms.vf2(g, make_ring(4))
-  expect_equal(length(subs), 24)
-})
diff --git a/tests/testthat/test-bug-501-rectangles.R b/tests/testthat/test-bug-501-rectangles.R
deleted file mode 100644
index 0b23738b43..0000000000
--- a/tests/testthat/test-bug-501-rectangles.R
+++ /dev/null
@@ -1,19 +0,0 @@
-test_that("Edges stop at outside of rectangle node", {
-  skip_if_not_installed("vdiffr")
-
-  rectangle_edges <- function() {
-    g <- make_graph(c(1, 2, 1, 4, 2, 1, 2, 5, 2, 3, 4, 1, 5, 2, 3, 2))
-    layout <- cbind(
-      c(-2.01, -1.16, -1.24, -2.74, -0.13),
-      c(1.27, 2.1, 3.14, 0.56, 2.01)
-    )
-    plot(g,
-      vertex.size = 30,
-      vertex.color = rgb(0.1, 0.7, 0.8, 0.1),
-      vertex.shape = "rectangle",
-      layout = layout
-    )
-  }
-
-  vdiffr::expect_doppelganger("rectangle-edges", rectangle_edges)
-})
diff --git a/tests/testthat/test-canonical.permutation.R b/tests/testthat/test-canonical.permutation.R
deleted file mode 100644
index 5edfe109fa..0000000000
--- a/tests/testthat/test-canonical.permutation.R
+++ /dev/null
@@ -1,18 +0,0 @@
-test_that("canonical_permutation works", {
-  g1 <- sample_gnm(10, 20)
-  cp1 <- canonical_permutation(g1)
-  cf1 <- permute(g1, cp1$labeling)
-
-  ## Do the same with a random permutation of it
-  g2 <- permute(g1, sample(vcount(g1)))
-  cp2 <- canonical_permutation(g2)
-  cf2 <- permute(g2, cp2$labeling)
-
-  ## Check that they are the same
-  el1 <- as_edgelist(cf1)
-  el2 <- as_edgelist(cf2)
-  el1 <- el1[order(el1[, 1], el1[, 2]), ]
-  el2 <- el2[order(el2[, 1], el2[, 2]), ]
-
-  expect_equal(el1, el2)
-})
diff --git a/tests/testthat/test-graph.isoclass.R b/tests/testthat/test-graph.isoclass.R
deleted file mode 100644
index f28a18af3d..0000000000
--- a/tests/testthat/test-graph.isoclass.R
+++ /dev/null
@@ -1,11 +0,0 @@
-test_that("isomorphism_class works", {
-  g1 <- graph_from_isomorphism_class(3, 10)
-  g2 <- graph_from_isomorphism_class(3, 11)
-  expect_equal(isomorphism_class(g1), 10)
-  expect_equal(isomorphism_class(g2), 11)
-
-  g1 <- add_vertices(g1, 3)
-  expect_equal(graph.isoclass.subgraph(g1, 1:3), 10)
-  expect_equal(graph.isoclass.subgraph(g1 %du% g2, 1:3), 10)
-  expect_equal(graph.isoclass.subgraph(g1 %du% g2, 7:9), 11)
-})
diff --git a/tests/testthat/test-graph.subisomorphic.lad.R b/tests/testthat/test-graph.subisomorphic.lad.R
deleted file mode 100644
index 964c518022..0000000000
--- a/tests/testthat/test-graph.subisomorphic.lad.R
+++ /dev/null
@@ -1,56 +0,0 @@
-test_that("graph.subisomorphic, method = 'lad' works", {
-  pattern <- graph_from_literal(
-    1:2:3:4:5,
-    1 - 2:5, 2 - 1:5:3, 3 - 2:4, 4 - 3:5, 5 - 4:2:1
-  )
-  target <- graph_from_literal(
-    1:2:3:4:5:6:7:8:9,
-    1 - 2:5:7, 2 - 1:5:3, 3 - 2:4, 4 - 3:5:6:8:9,
-    5 - 1:2:4:6:7, 6 - 7:5:4:9, 7 - 1:5:6,
-    8 - 4:9, 9 - 6:4:8
-  )
-  domains <- list(
-    `1` = c(1, 3, 9), `2` = c(5, 6, 7, 8), `3` = c(2, 4, 6, 7, 8, 9),
-    `4` = c(1, 3, 9), `5` = c(2, 4, 8, 9)
-  )
-  i1 <- subgraph_isomorphic(pattern, target, method = "lad")
-  i2 <- subgraph_isomorphic(pattern, target, induced = TRUE, method = "lad")
-  i3 <- subgraph_isomorphic(pattern, target,
-    domains = domains,
-    method = "lad"
-  )
-
-  expect_true(i1)
-  expect_true(i2)
-  expect_true(i3)
-})
-
-test_that("LAD stress test", {
-  local_rng_version("3.5.0")
-  withr::local_seed(42)
-  N <- 100
-
-  for (i in 1:N) {
-    target <- sample_gnp(20, .5)
-    pn <- sample(4:18, 1)
-    pattern <- induced_subgraph(target, sample(vcount(target), pn))
-    iso <- subgraph_isomorphic(pattern, target,
-      induced = TRUE,
-      method = "lad"
-    )
-    expect_true(iso)
-  }
-
-  withr::local_seed(42)
-
-  for (i in 1:N) {
-    target <- sample_gnp(20, 1 / 20)
-    pn <- sample(5:18, 1)
-    pattern <- sample_gnp(pn, .6)
-    iso <- subgraph_isomorphic(pattern, target,
-      induced = TRUE,
-      method = "lad"
-    )
-    expect_false(iso)
-  }
-})
diff --git a/tests/testthat/test-graph.subisomorphic.vf2.R b/tests/testthat/test-graph.subisomorphic.vf2.R
deleted file mode 100644
index 3b41375134..0000000000
--- a/tests/testthat/test-graph.subisomorphic.vf2.R
+++ /dev/null
@@ -1,18 +0,0 @@
-test_that("graph.subisomorphic.vf2 works", {
-  withr::local_seed(42)
-
-  g1 <- sample_gnp(20, 6 / 20)
-  g2 <- sample_gnp(20, 6 / 20)
-  g <- g1 %du% g2
-
-  ig1 <- graph.subisomorphic.vf2(g, g1)
-  ig2 <- graph.subisomorphic.vf2(g, g2)
-
-  expect_true(ig1$iso)
-  expect_equal(ig1$map12, c(1:vcount(g1), rep(0, vcount(g2))))
-  expect_equal(ig1$map21, 1:vcount(g1))
-
-  expect_true(ig2$iso)
-  expect_equal(ig2$map12, c(rep(0, vcount(g1)), 1:vcount(g2)))
-  expect_equal(ig2$map21, 1:vcount(g2) + vcount(g1))
-})
diff --git a/tests/testthat/test-isomorphism.R b/tests/testthat/test-isomorphism.R
deleted file mode 100644
index 4fb497ccfa..0000000000
--- a/tests/testthat/test-isomorphism.R
+++ /dev/null
@@ -1,148 +0,0 @@
-test_that("isomorphic", {
-  g <- graph_from_literal(A - B - C - A)
-  expect_isomorphic(g, g)
-  expect_isomorphic(g, g, method = "direct")
-  expect_isomorphic(g, g, method = "vf2")
-  expect_isomorphic(g, g, method = "bliss")
-
-  g2 <- graph_from_literal(A - B - C)
-  expect_not_isomorphic(g, g2)
-  expect_not_isomorphic(g, g2, method = "direct")
-  expect_not_isomorphic(g, g2, method = "vf2")
-  expect_not_isomorphic(g, g2, method = "bliss")
-})
-
-test_that("subgraph_isomorphic", {
-  g <- graph_from_literal(A - B - C - D - E - A)
-  g2 <- graph_from_literal(A - B - C - D)
-
-  expect_true(subgraph_isomorphic(g2, g))
-  expect_true(subgraph_isomorphic(g2, g, method = "vf2"))
-  expect_true(subgraph_isomorphic(g2, g, method = "lad"))
-
-  g3 <- graph_from_literal(A - B - C - A)
-  expect_false(subgraph_isomorphic(g3, g))
-  expect_false(subgraph_isomorphic(g3, g, method = "vf2"))
-  expect_false(subgraph_isomorphic(g3, g, method = "lad"))
-})
-
-test_that("count_isomorphisms", {
-  g <- graph_from_literal(A - B - C - D - A)
-  expect_equal(count_isomorphisms(g, g), 8)
-
-  g2 <- graph_from_literal(A - B - C - A)
-  expect_equal(count_isomorphisms(g, g2), 0)
-})
-
-test_that("count_isomorphisms_with_colors", {
-  expect_equal(
-    count_isomorphisms(make_ring(3),
-      make_ring(3),
-      edge.color1 = c(2, 2, 2),
-      edge.color2 = c(2, 2, 2),
-      vertex.color1 = c(3, 3, 3),
-      vertex.color2 = c(3, 3, 3),
-      method = "vf2"
-    ),
-    6
-  )
-
-  expect_equal(
-    count_isomorphisms(make_ring(3),
-      make_ring(3),
-      edge.color1 = c(2, 2, 2),
-      edge.color2 = c(2, 2, 2),
-      vertex.color1 = c(1, 2, 3),
-      vertex.color2 = c(1, 2, 3),
-      method = "vf2"
-    ),
-    1
-  )
-
-  expect_equal(
-    count_isomorphisms(make_ring(3),
-      make_ring(3),
-      edge.color1 = c(2, 2, 3),
-      edge.color2 = c(3, 2, 2),
-      vertex.color1 = c(3, 3, 3),
-      vertex.color2 = c(3, 3, 3),
-      method = "vf2"
-    ),
-    2
-  )
-})
-
-test_that("count_subgraph_isomorphisms", {
-  g <- graph_from_literal(A - B - C - D - A)
-  g2 <- graph_from_literal(A - B - C - D)
-
-  expect_equal(count_subgraph_isomorphisms(g2, g, method = "lad"), 8)
-  expect_equal(count_subgraph_isomorphisms(g2, g, method = "vf2"), 8)
-
-  g3 <- graph_from_literal(A - B - C - A)
-  expect_equal(count_subgraph_isomorphisms(g3, g, method = "lad"), 0)
-  expect_equal(count_subgraph_isomorphisms(g3, g, method = "vf2"), 0)
-})
-
-test_that("isomorphisms", {
-  g <- graph_from_literal(A - B - C - D - A)
-  g2 <- graph_from_literal(W - X - Y - Z - W)
-
-  res <- list(
-    V(g2)[1, 2, 3, 4],
-    V(g2)[1, 4, 3, 2],
-    V(g2)[2, 1, 4, 3],
-    V(g2)[2, 3, 4, 1],
-    V(g2)[3, 2, 1, 4],
-    V(g2)[3, 4, 1, 2],
-    V(g2)[4, 1, 2, 3],
-    V(g2)[4, 3, 2, 1]
-  )
-
-  expect_equal(ignore_attr = TRUE, isomorphisms(g, g2), res)
-
-  g3 <- graph_from_literal(X - Y - Z - X)
-  expect_equal(isomorphisms(g, g3), list())
-})
-
-test_that("subgraph_isomorphisms, lad", {
-  g <- graph_from_literal(A - B - C - D - A)
-  g2 <- graph_from_literal(Z - X - Y)
-
-  res <- list(
-    V(g)[1, 4, 3],
-    V(g)[1, 2, 3],
-    V(g)[2, 1, 4],
-    V(g)[2, 3, 4],
-    V(g)[3, 2, 1],
-    V(g)[3, 4, 1],
-    V(g)[4, 3, 2],
-    V(g)[4, 1, 2]
-  )
-
-  expect_equal(ignore_attr = TRUE, subgraph_isomorphisms(g2, g, method = "lad"), res)
-
-  g3 <- graph_from_literal(X - Y - Z - X)
-  expect_equal(subgraph_isomorphisms(g3, g, method = "lad"), list())
-})
-
-test_that("subgraph_isomorphisms, vf2", {
-  g <- graph_from_literal(A - B - C - D - A)
-  g2 <- graph_from_literal(Z - X - Y)
-
-  res <- list(
-    V(g)[1, 2, 3],
-    V(g)[1, 4, 3],
-    V(g)[2, 1, 4],
-    V(g)[2, 3, 4],
-    V(g)[3, 2, 1],
-    V(g)[3, 4, 1],
-    V(g)[4, 1, 2],
-    V(g)[4, 3, 2]
-  )
-
-  expect_equal(ignore_attr = TRUE, subgraph_isomorphisms(g2, g, method = "vf2"), res)
-
-  g3 <- graph_from_literal(X - Y - Z - X)
-  expect_equal(subgraph_isomorphisms(g3, g, method = "vf2"), list())
-})
diff --git a/tests/testthat/test-notable.R b/tests/testthat/test-notable.R
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/tests/testthat/test-plot.R b/tests/testthat/test-plot.R
index 5246e4a522..0874cc09d3 100644
--- a/tests/testthat/test-plot.R
+++ b/tests/testthat/test-plot.R
@@ -109,3 +109,23 @@ test_that("label colors are correct when loops are present", {
     }
   )
 })
+
+test_that("Edges stop at outside of rectangle node", {
+  skip_if_not_installed("vdiffr")
+
+  rectangle_edges <- function() {
+    g <- make_graph(c(1, 2, 1, 4, 2, 1, 2, 5, 2, 3, 4, 1, 5, 2, 3, 2))
+    layout <- cbind(
+      c(-2.01, -1.16, -1.24, -2.74, -0.13),
+      c(1.27, 2.1, 3.14, 0.56, 2.01)
+    )
+    plot(g,
+      vertex.size = 30,
+      vertex.color = rgb(0.1, 0.7, 0.8, 0.1),
+      vertex.shape = "rectangle",
+      layout = layout
+    )
+  }
+
+  vdiffr::expect_doppelganger("rectangle-edges", rectangle_edges)
+})
diff --git a/tests/testthat/test-topology.R b/tests/testthat/test-topology.R
index 25a96b3b81..527a8de74a 100644
--- a/tests/testthat/test-topology.R
+++ b/tests/testthat/test-topology.R
@@ -1,9 +1,9 @@
 test_that("automorphisms works", {
-  g <- make_ring(10)
-  expect_equal(count_automorphisms(g)$group_size, "20")
+  ring <- make_ring(10)
+  expect_equal(count_automorphisms(ring)$group_size, "20")
 
-  g <- make_full_graph(4)
-  expect_equal(count_automorphisms(g)$group_size, "24")
+  full <- make_full_graph(4)
+  expect_equal(count_automorphisms(full)$group_size, "24")
 })
 
 
@@ -18,51 +18,41 @@ test_that("automorphisms works with colored graphs", {
 
 
 test_that("automorphism_group works", {
-  g <- make_ring(10)
-  aut <- lapply(automorphism_group(g), as.vector)
-  aut <- aut[order(sapply(aut, "[[", 1))]
-  expect_equal(aut, list(c(1, 10:2), c(2:10, 1)))
+  ring <- make_ring(10)
+  aut_ring <- lapply(automorphism_group(ring), as.vector)
+  aut_ring <- aut_ring[order(sapply(aut_ring, "[[", 1))]
+  expect_equal(aut_ring, list(c(1, 10:2), c(2:10, 1)))
 
-  g <- make_full_graph(4)
-  aut <- lapply(automorphism_group(g), as.vector)
-  aut <- aut[order(sapply(aut, "[[", 1))]
-  expect_equal(aut, list(c(1, 2, 4, 3), c(1, 3, 2, 4), c(2, 1, 3, 4)))
+  full <- make_full_graph(4)
+  aut_full <- lapply(automorphism_group(full), as.vector)
+  aut_full <- aut_full[order(sapply(aut_full, "[[", 1))]
+  expect_equal(aut_full, list(c(1, 2, 4, 3), c(1, 3, 2, 4), c(2, 1, 3, 4)))
 })
 
 
 test_that("automorphism_group works with colored graphs", {
-  g <- make_full_graph(4)
-  aut <- lapply(automorphism_group(g, colors = c(1, 2, 1, 2)), as.vector)
-  aut <- aut[order(sapply(aut, "[[", 1))]
-  expect_equal(aut, list(c(1, 4, 3, 2), c(3, 2, 1, 4)))
+  full <- make_full_graph(4)
+  aut_full <- lapply(automorphism_group(full, colors = c(1, 2, 1, 2)), as.vector)
+  aut_full <- aut_full[order(sapply(aut_full, "[[", 1))]
+  expect_equal(aut_full, list(c(1, 4, 3, 2), c(3, 2, 1, 4)))
 
-  V(g)$color <- c(1, 2, 1, 2)
-  aut <- lapply(automorphism_group(g), as.vector)
-  aut <- aut[order(sapply(aut, "[[", 1))]
-  expect_equal(aut, list(c(1, 4, 3, 2), c(3, 2, 1, 4)))
-})
-
-test_that("isomorphisms works", {
-  motif <- make_empty_graph(directed = FALSE) +
-    vertices("D1", "D2", type = c("type1", "type1")) +
-    edges("D1", "D2", type = c("type2"))
-  subgraph_isomorphisms(
-    target = motif, pattern = motif, method = "vf2",
-    vertex.color1 = 2:1, vertex.color2 = 1:2
-  )
+  V(full)$color <- c(1, 2, 1, 2)
+  aut_full_col <- lapply(automorphism_group(full), as.vector)
+  aut_full_col <- aut_full_col[order(sapply(aut_full_col, "[[", 1))]
+  expect_equal(aut_full_col, list(c(1, 4, 3, 2), c(3, 2, 1, 4)))
 })
 
 test_that("isomorphisms() works", {
   motif <- make_empty_graph(directed = FALSE) +
     vertices("D1", "D2", type = c("type1", "type1")) +
     edges("D1", "D2", type = c("type2"))
-  out <- isomorphisms(
+  motif_iso <- isomorphisms(
     motif, motif,
     method = "vf2",
     vertex.color1 = 2:1, vertex.color2 = 1:2
   )
-  expect_length(out, 1)
-  expect_equal(as.numeric(out[[1]]), 2:1)
+  expect_length(motif_iso, 1)
+  expect_equal(as.numeric(motif_iso[[1]]), 2:1)
 })
 
 test_that("subgraph_isomorphisms works", {
@@ -76,3 +66,275 @@ test_that("subgraph_isomorphisms works", {
   expect_length(out, 1)
   expect_equal(as.numeric(out[[1]]), 2:1)
 })
+
+test_that("graph.get.subisomorphisms.vf2() works even if the graph has a vertex attribute named x", {
+  g <- make_full_graph(4)
+  V(g)$x <- 1:4
+  subs <- graph.get.subisomorphisms.vf2(g, make_ring(4))
+  expect_equal(length(subs), 24)
+})
+
+test_that("VF2 isomorphism considers colors", {
+  full <- make_full_graph(3)
+  path <- make_ring(3, circular = FALSE)
+  V(full)$color <- c(1, 1, 2)
+  V(path)$color <- c(1, 2, 1)
+  n <- count_subgraph_isomorphisms(path, full, method = "vf2")
+  expect_equal(n, 2)
+})
+
+test_that("canonical_permutation works", {
+  g1 <- sample_gnm(10, 20)
+  cp1 <- canonical_permutation(g1)
+  cf1 <- permute(g1, cp1$labeling)
+
+  ## Do the same with a random permutation of it
+  g2 <- permute(g1, sample(vcount(g1)))
+  cp2 <- canonical_permutation(g2)
+  cf2 <- permute(g2, cp2$labeling)
+
+  ## Check that they are the same
+  el1 <- as_edgelist(cf1)
+  el2 <- as_edgelist(cf2)
+  el1 <- el1[order(el1[, 1], el1[, 2]), ]
+  el2 <- el2[order(el2[, 1], el2[, 2]), ]
+
+  expect_equal(el1, el2)
+})
+
+test_that("isomorphism_class works", {
+  g_iso10 <- graph_from_isomorphism_class(3, 10)
+  g_iso11 <- graph_from_isomorphism_class(3, 11)
+  expect_equal(isomorphism_class(g_iso10), 10)
+  expect_equal(isomorphism_class(g_iso11), 11)
+
+  g_iso10_1 <- add_vertices(g_iso10, 3)
+  expect_equal(graph.isoclass.subgraph(g_iso10_1, 1:3), 10)
+  expect_equal(graph.isoclass.subgraph(g_iso10_1 %du% g_iso11, 1:3), 10)
+  expect_equal(graph.isoclass.subgraph(g_iso10_1 %du% g_iso11, 7:9), 11)
+})
+
+test_that("graph.subisomorphic, method = 'lad' works", {
+  pattern <- graph_from_literal(
+    1:2:3:4:5,
+    1 - 2:5, 2 - 1:5:3, 3 - 2:4, 4 - 3:5, 5 - 4:2:1
+  )
+  target <- graph_from_literal(
+    1:2:3:4:5:6:7:8:9,
+    1 - 2:5:7, 2 - 1:5:3, 3 - 2:4, 4 - 3:5:6:8:9,
+    5 - 1:2:4:6:7, 6 - 7:5:4:9, 7 - 1:5:6,
+    8 - 4:9, 9 - 6:4:8
+  )
+  domains <- list(
+    `1` = c(1, 3, 9), `2` = c(5, 6, 7, 8), `3` = c(2, 4, 6, 7, 8, 9),
+    `4` = c(1, 3, 9), `5` = c(2, 4, 8, 9)
+  )
+  sub_iso1 <- subgraph_isomorphic(pattern, target, method = "lad")
+  sub_iso2 <- subgraph_isomorphic(pattern, target, induced = TRUE, method = "lad")
+  sub_iso3 <- subgraph_isomorphic(pattern, target,
+    domains = domains,
+    method = "lad"
+  )
+
+  expect_true(sub_iso1)
+  expect_true(sub_iso2)
+  expect_true(sub_iso3)
+})
+
+test_that("LAD stress test", {
+  local_rng_version("3.5.0")
+  withr::local_seed(42)
+  N <- 100
+
+  for (i in 1:N) {
+    target <- sample_gnp(20, .5)
+    pn <- sample(4:18, 1)
+    pattern <- induced_subgraph(target, sample(vcount(target), pn))
+    iso <- subgraph_isomorphic(pattern, target,
+      induced = TRUE,
+      method = "lad"
+    )
+    expect_true(iso)
+  }
+
+  withr::local_seed(42)
+
+  for (i in 1:N) {
+    target <- sample_gnp(20, 1 / 20)
+    pn <- sample(5:18, 1)
+    pattern <- sample_gnp(pn, .6)
+    iso <- subgraph_isomorphic(pattern, target,
+      induced = TRUE,
+      method = "lad"
+    )
+    expect_false(iso)
+  }
+})
+
+test_that("graph.subisomorphic.vf2 works", {
+  withr::local_seed(42)
+
+  gnp1 <- sample_gnp(20, 6 / 20)
+  gnp2 <- sample_gnp(20, 6 / 20)
+  g <- gnp1 %du% gnp2
+
+  g1_iso <- graph.subisomorphic.vf2(g, gnp1)
+
+  expect_true(g1_iso$iso)
+  expect_equal(g1_iso$map12, c(1:vcount(gnp1), rep(0, vcount(gnp2))))
+  expect_equal(g1_iso$map21, 1:vcount(gnp1))
+
+  g2_iso <- graph.subisomorphic.vf2(g, gnp2)
+  expect_true(g2_iso$iso)
+  expect_equal(g2_iso$map12, c(rep(0, vcount(gnp1)), 1:vcount(gnp2)))
+  expect_equal(g2_iso$map21, 1:vcount(gnp2) + vcount(gnp1))
+})
+
+test_that("isomorphic", {
+  g1 <- graph_from_literal(A - B - C - A)
+  expect_isomorphic(g1, g1)
+  expect_isomorphic(g1, g1, method = "direct")
+  expect_isomorphic(g1, g1, method = "vf2")
+  expect_isomorphic(g1, g1, method = "bliss")
+
+  g2 <- graph_from_literal(A - B - C)
+  expect_not_isomorphic(g1, g2)
+  expect_not_isomorphic(g1, g2, method = "direct")
+  expect_not_isomorphic(g1, g2, method = "vf2")
+  expect_not_isomorphic(g1, g2, method = "bliss")
+})
+
+test_that("subgraph_isomorphic", {
+  g1 <- graph_from_literal(A - B - C - D - E - A)
+  g2 <- graph_from_literal(A - B - C - D)
+
+  expect_true(subgraph_isomorphic(g2, g1))
+  expect_true(subgraph_isomorphic(g2, g1, method = "vf2"))
+  expect_true(subgraph_isomorphic(g2, g1, method = "lad"))
+
+  g3 <- graph_from_literal(A - B - C - A)
+  expect_false(subgraph_isomorphic(g3, g1))
+  expect_false(subgraph_isomorphic(g3, g1, method = "vf2"))
+  expect_false(subgraph_isomorphic(g3, g1, method = "lad"))
+})
+
+test_that("count_isomorphisms", {
+  g1 <- graph_from_literal(A - B - C - D - A)
+  expect_equal(count_isomorphisms(g1, g1), 8)
+
+  g2 <- graph_from_literal(A - B - C - A)
+  expect_equal(count_isomorphisms(g1, g2), 0)
+})
+
+test_that("count_isomorphisms_with_colors", {
+  expect_equal(
+    count_isomorphisms(make_ring(3),
+      make_ring(3),
+      edge.color1 = c(2, 2, 2),
+      edge.color2 = c(2, 2, 2),
+      vertex.color1 = c(3, 3, 3),
+      vertex.color2 = c(3, 3, 3),
+      method = "vf2"
+    ),
+    6
+  )
+
+  expect_equal(
+    count_isomorphisms(make_ring(3),
+      make_ring(3),
+      edge.color1 = c(2, 2, 2),
+      edge.color2 = c(2, 2, 2),
+      vertex.color1 = c(1, 2, 3),
+      vertex.color2 = c(1, 2, 3),
+      method = "vf2"
+    ),
+    1
+  )
+
+  expect_equal(
+    count_isomorphisms(make_ring(3),
+      make_ring(3),
+      edge.color1 = c(2, 2, 3),
+      edge.color2 = c(3, 2, 2),
+      vertex.color1 = c(3, 3, 3),
+      vertex.color2 = c(3, 3, 3),
+      method = "vf2"
+    ),
+    2
+  )
+})
+
+test_that("count_subgraph_isomorphisms", {
+  g1 <- graph_from_literal(A - B - C - D - A)
+  g2 <- graph_from_literal(A - B - C - D)
+
+  expect_equal(count_subgraph_isomorphisms(g2, g1, method = "lad"), 8)
+  expect_equal(count_subgraph_isomorphisms(g2, g1, method = "vf2"), 8)
+
+  g3 <- graph_from_literal(A - B - C - A)
+  expect_equal(count_subgraph_isomorphisms(g3, g1, method = "lad"), 0)
+  expect_equal(count_subgraph_isomorphisms(g3, g1, method = "vf2"), 0)
+})
+
+test_that("isomorphisms", {
+  g1 <- graph_from_literal(A - B - C - D - A)
+  g2 <- graph_from_literal(W - X - Y - Z - W)
+
+  res <- list(
+    V(g2)[1, 2, 3, 4],
+    V(g2)[1, 4, 3, 2],
+    V(g2)[2, 1, 4, 3],
+    V(g2)[2, 3, 4, 1],
+    V(g2)[3, 2, 1, 4],
+    V(g2)[3, 4, 1, 2],
+    V(g2)[4, 1, 2, 3],
+    V(g2)[4, 3, 2, 1]
+  )
+
+  expect_equal(ignore_attr = TRUE, isomorphisms(g1, g2), res)
+
+  g3 <- graph_from_literal(X - Y - Z - X)
+  expect_equal(isomorphisms(g1, g3), list())
+})
+
+test_that("subgraph_isomorphisms, lad", {
+  g1 <- graph_from_literal(A - B - C - D - A)
+  g2 <- graph_from_literal(Z - X - Y)
+
+  res <- list(
+    V(g1)[1, 4, 3],
+    V(g1)[1, 2, 3],
+    V(g1)[2, 1, 4],
+    V(g1)[2, 3, 4],
+    V(g1)[3, 2, 1],
+    V(g1)[3, 4, 1],
+    V(g1)[4, 3, 2],
+    V(g1)[4, 1, 2]
+  )
+
+  expect_equal(ignore_attr = TRUE, subgraph_isomorphisms(g2, g1, method = "lad"), res)
+
+  g3 <- graph_from_literal(X - Y - Z - X)
+  expect_equal(subgraph_isomorphisms(g3, g1, method = "lad"), list())
+})
+
+test_that("subgraph_isomorphisms, vf2", {
+  g1 <- graph_from_literal(A - B - C - D - A)
+  g2 <- graph_from_literal(Z - X - Y)
+
+  res <- list(
+    V(g1)[1, 2, 3],
+    V(g1)[1, 4, 3],
+    V(g1)[2, 1, 4],
+    V(g1)[2, 3, 4],
+    V(g1)[3, 2, 1],
+    V(g1)[3, 4, 1],
+    V(g1)[4, 1, 2],
+    V(g1)[4, 3, 2]
+  )
+
+  expect_equal(ignore_attr = TRUE, subgraph_isomorphisms(g2, g1, method = "vf2"), res)
+
+  g3 <- graph_from_literal(X - Y - Z - X)
+  expect_equal(subgraph_isomorphisms(g3, g1, method = "vf2"), list())
+})