From 1064771c047a9342e36920717e79e796859fce62 Mon Sep 17 00:00:00 2001
From: schochastics <david@schochastics.net>
Date: Sat, 8 Feb 2025 19:47:16 +0100
Subject: [PATCH 1/8] merged and refactored flow.R tests

---
 R/flow.R                                      |  73 ++-----
 .../{minimal.st.separators.md => flow.md}     |   0
 tests/testthat/test-all.st.cuts.R             |  21 --
 tests/testthat/test-bug-1033045.R             |   6 -
 tests/testthat/test-dominator.tree.R          |  21 --
 tests/testthat/test-edge.connectivity.R       |  39 ----
 tests/testthat/test-flow.R                    | 205 ++++++++++++++++++
 tests/testthat/test-graph.maxflow.R           |  11 -
 tests/testthat/test-graph.mincut.R            |  21 --
 tests/testthat/test-minimal.st.separators.R   |  16 --
 tests/testthat/test-minimum.size.separators.R |  19 --
 11 files changed, 224 insertions(+), 208 deletions(-)
 rename tests/testthat/_snaps/{minimal.st.separators.md => flow.md} (100%)
 delete mode 100644 tests/testthat/test-all.st.cuts.R
 delete mode 100644 tests/testthat/test-bug-1033045.R
 delete mode 100644 tests/testthat/test-dominator.tree.R
 delete mode 100644 tests/testthat/test-edge.connectivity.R
 create mode 100644 tests/testthat/test-flow.R
 delete mode 100644 tests/testthat/test-graph.maxflow.R
 delete mode 100644 tests/testthat/test-graph.mincut.R
 delete mode 100644 tests/testthat/test-minimal.st.separators.R
 delete mode 100644 tests/testthat/test-minimum.size.separators.R

diff --git a/R/flow.R b/R/flow.R
index 607e70dc1ff..1fb693b503e 100644
--- a/R/flow.R
+++ b/R/flow.R
@@ -1,4 +1,3 @@
-
 #' Vertex connectivity
 #'
 #' @description
@@ -287,27 +286,21 @@ dominator.tree <- function(graph, root, mode = c("out", "in", "all", "total")) {
 #' @export
 min_cut <- function(graph, source = NULL, target = NULL, capacity = NULL, value.only = TRUE) {
   ensure_igraph(graph)
-  if (is.null(capacity)) {
-    if ("capacity" %in% edge_attr_names(graph)) {
-      capacity <- E(graph)$capacity
-    }
-  }
-  if (length(source) == 0) {
-    source <- NULL
+  if (is.null(capacity) && "capacity" %in% edge_attr_names(graph)) {
+    capacity <- E(graph)$capacity
   }
-  if (length(target) == 0) {
-    target <- NULL
-  }
-  if (is.null(source) && !is.null(target) ||
-    is.null(target) && !is.null(source)) {
-    stop("Please give both source and target or neither")
+
+  if (xor(is.null(source), is.null(target))) {
+    cli::cli_abort("Please give both source and target or neither")
   }
+
   if (!is.null(capacity)) {
     capacity <- as.numeric(capacity)
   }
 
   value.only <- as.logical(value.only)
   on.exit(.Call(R_igraph_finalizer))
+
   if (is.null(target) && is.null(source)) {
     if (value.only) {
       res <- .Call(R_igraph_mincut_value, graph, capacity)
@@ -430,13 +423,6 @@ min_cut <- function(graph, source = NULL, target = NULL, capacity = NULL, value.
 vertex_connectivity <- function(graph, source = NULL, target = NULL, checks = TRUE) {
   ensure_igraph(graph)
 
-  if (length(source) == 0) {
-    source <- NULL
-  }
-  if (length(target) == 0) {
-    target <- NULL
-  }
-
   if (is.null(source) && is.null(target)) {
     on.exit(.Call(R_igraph_finalizer))
     .Call(R_igraph_vertex_connectivity, graph, as.logical(checks))
@@ -534,13 +520,6 @@ vertex_connectivity <- function(graph, source = NULL, target = NULL, checks = TR
 edge_connectivity <- function(graph, source = NULL, target = NULL, checks = TRUE) {
   ensure_igraph(graph)
 
-  if (length(source) == 0) {
-    source <- NULL
-  }
-  if (length(target) == 0) {
-    target <- NULL
-  }
-
   if (is.null(source) && is.null(target)) {
     on.exit(.Call(R_igraph_finalizer))
     .Call(R_igraph_edge_connectivity, graph, as.logical(checks))
@@ -551,22 +530,15 @@ edge_connectivity <- function(graph, source = NULL, target = NULL, checks = TRUE
       as_igraph_vs(graph, source) - 1, as_igraph_vs(graph, target) - 1
     )
   } else {
-    stop("either give both source and target or neither")
+    cli::cli_abort("Either give both source and target or neither")
   }
 }
 
 #' @rdname edge_connectivity
 #' @export
-edge_disjoint_paths <- function(graph, source, target) {
+edge_disjoint_paths <- function(graph, source = NULL, target = NULL) {
   ensure_igraph(graph)
 
-  if (length(source) == 0) {
-    source <- NULL
-  }
-  if (length(target) == 0) {
-    target <- NULL
-  }
-
   on.exit(.Call(R_igraph_finalizer))
   .Call(
     R_igraph_edge_disjoint_paths, graph,
@@ -579,13 +551,6 @@ edge_disjoint_paths <- function(graph, source, target) {
 vertex_disjoint_paths <- function(graph, source = NULL, target = NULL) {
   ensure_igraph(graph)
 
-  if (length(source) == 0) {
-    source <- NULL
-  }
-  if (length(target) == 0) {
-    target <- NULL
-  }
-
   on.exit(.Call(R_igraph_finalizer))
   .Call(
     R_igraph_vertex_disjoint_paths, graph, as_igraph_vs(graph, source) - 1,
@@ -638,13 +603,13 @@ cohesion.igraph <- function(x, checks = TRUE, ...) {
 #' @examples
 #'
 #' # A very simple graph
-#' g <- graph_from_literal(a -+ b -+ c -+ d -+ e)
+#' g <- graph_from_literal(a - +b - +c - +d - +e)
 #' st_cuts(g, source = "a", target = "e")
 #'
 #' # A somewhat more difficult graph
 #' g2 <- graph_from_literal(
-#'   s --+ a:b, a:b --+ t,
-#'   a --+ 1:2:3, 1:2:3 --+ b
+#'   s - -+a:b, a:b - -+t,
+#'   a - -+1:2:3, 1:2:3 - -+b
 #' )
 #' st_cuts(g2, source = "s", target = "t")
 #' @family flow
@@ -693,8 +658,8 @@ st_cuts <- all_st_cuts_impl
 #'
 #' # A difficult graph, from the Provan-Shier paper
 #' g <- graph_from_literal(
-#'   s --+ a:b, a:b --+ t,
-#'   a --+ 1:2:3:4:5, 1:2:3:4:5 --+ b
+#'   s - -+a:b, a:b - -+t,
+#'   a - -+1:2:3:4:5, 1:2:3:4:5 - -+b
 #' )
 #' st_min_cuts(g, source = "s", target = "t")
 #' @family flow
@@ -746,9 +711,9 @@ st_min_cuts <- all_st_mincuts_impl
 #'
 #' ## The example from the paper
 #' g <- graph_from_literal(
-#'   R -+ A:B:C, A -+ D, B -+ A:D:E, C -+ F:G, D -+ L,
-#'   E -+ H, F -+ I, G -+ I:J, H -+ E:K, I -+ K, J -+ I,
-#'   K -+ I:R, L -+ H
+#'   R - +A:B:C, A - +D, B - +A:D:E, C - +F:G, D - +L,
+#'   E - +H, F - +I, G - +I:J, H - +E:K, I - +K, J - +I,
+#'   K - +I:R, L - +H
 #' )
 #' dtree <- dominator_tree(g, root = "R")
 #' layout <- layout_as_tree(dtree$domtree, root = "R")
@@ -758,10 +723,10 @@ st_min_cuts <- all_st_mincuts_impl
 #' @export
 dominator_tree <- function(graph, root, mode = c("out", "in", "all", "total")) {
   # Argument checks
- ensure_igraph(graph)
+  ensure_igraph(graph)
   root <- as_igraph_vs(graph, root)
   if (length(root) == 0) {
-    stop("No vertex was specified")
+    cli::cli_abort("No vertex was specified")
   }
   mode <- switch(igraph.match.arg(mode),
     "out" = 1,
diff --git a/tests/testthat/_snaps/minimal.st.separators.md b/tests/testthat/_snaps/flow.md
similarity index 100%
rename from tests/testthat/_snaps/minimal.st.separators.md
rename to tests/testthat/_snaps/flow.md
diff --git a/tests/testthat/test-all.st.cuts.R b/tests/testthat/test-all.st.cuts.R
deleted file mode 100644
index 60563baec61..00000000000
--- a/tests/testthat/test-all.st.cuts.R
+++ /dev/null
@@ -1,21 +0,0 @@
-test_that("all.st.cuts works", {
-
-  g <- graph_from_literal(a - +b - +c - +d - +e)
-  cc <- st_cuts(g, source = "a", target = "e")
-  expect_equal(unvs(cc$cuts), list(1, 2, 3, 4))
-  expect_equal(unvs(cc$partition1s), list(1, 1:2, 1:3, 1:4))
-
-  g2 <- graph_from_literal(s - +a:b - +t, a - +1:2:3 - +b)
-  cc <- st_cuts(g2, source = "s", target = "t")
-  expect_equal(unvs(cc$cuts), list(c(1, 2), c(1, 7), c(2, 3, 4, 5, 6), c(2, 3, 4, 5, 10), c(2, 3, 4, 6, 9), c(2, 3, 4, 9, 10), c(2, 3, 5, 6, 8), c(2, 3, 5, 8, 10), c(2, 3, 6, 8, 9), c(2, 3, 8, 9, 10), c(3, 7)))
-  expect_equal(
-    unvs(cc$partition1s),
-    list(1, c(1, 3), c(1, 2), c(1, 2, 7), c(1, 2, 6), c(1, 2, 6, 7), c(1, 2, 5), c(1, 2, 5, 7), c(1, 2, 5, 6), c(1, 2, 5, 6, 7), c(1, 2, 5, 6, 7, 3))
-  )
-
-  g3 <- graph_from_literal(s - +a:b - +t, a - +1:2:3:4:5 - +b)
-  cc <- st_min_cuts(g3, source = "s", target = "t")
-  expect_equal(cc$value, 2)
-  expect_equal(unvs(cc$cuts), list(c(1, 2), c(1, 9), c(3, 9)))
-  expect_equal(unvs(cc$partition1s), list(1, c(1, 3), c(1, 3, 2, 9, 8, 7, 6, 5)))
-})
diff --git a/tests/testthat/test-bug-1033045.R b/tests/testthat/test-bug-1033045.R
deleted file mode 100644
index 3b220297866..00000000000
--- a/tests/testthat/test-bug-1033045.R
+++ /dev/null
@@ -1,6 +0,0 @@
-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))
-})
diff --git a/tests/testthat/test-dominator.tree.R b/tests/testthat/test-dominator.tree.R
deleted file mode 100644
index dba7eeadf18..00000000000
--- a/tests/testthat/test-dominator.tree.R
+++ /dev/null
@@ -1,21 +0,0 @@
-test_that("dominator_tree works", {
-  g <- graph_from_literal(
-    R - +A:B:C, A - +D, B - +A:D:E, C - +F:G, D - +L,
-    E - +H, F - +I, G - +I:J, H - +E:K, I - +K, J - +I,
-    K - +I:R, L - +H
-  )
-  dtree <- dominator_tree(g, root = "R")
-
-  # This is awkward; dtree$dom contains -1 for the root and normal vertex indices
-  # for the rest, and we want to map them to names. This seemed to be the cleanest
-  # way, but it is not nearly as user-friendly as it should be
-  names <- c("$root", V(g)$name)
-  dtree$dom <- names[ifelse(dtree$dom < 0, 1, dtree$dom + 1)]
-  dtree$leftout <- V(g)$name[dtree$leftout]
-  expect_equal(dtree$dom, c("$root", "R", "R", "R", "R", "R", "C", "C", "D", "R", "R", "G", "R"))
-  expect_equal(dtree$leftout, character())
-  expect_equal(
-    as_edgelist(dtree$domtree),
-    structure(c("R", "R", "R", "R", "R", "C", "C", "D", "R", "R", "G", "R", "A", "B", "C", "D", "E", "F", "G", "L", "H", "I", "J", "K"), .Dim = c(12L, 2L))
-  )
-})
diff --git a/tests/testthat/test-edge.connectivity.R b/tests/testthat/test-edge.connectivity.R
deleted file mode 100644
index 274245cc986..00000000000
--- a/tests/testthat/test-edge.connectivity.R
+++ /dev/null
@@ -1,39 +0,0 @@
-test_that("edge_connectivity works", {
-
-  g <- largest_component(sample_gnp(30, 8 / 30))
-  ec <- edge_connectivity(g)
-  ecST <- Inf
-  for (j in 1:(vcount(g) - 1)) {
-    for (k in (j + 1):vcount(g)) {
-      ec2 <- edge_connectivity(g, source = j, target = k)
-      if (ec2 < ecST) {
-        ecST <- ec2
-      }
-    }
-  }
-  expect_equal(ec, ecST)
-
-})
-
-test_that("edge_connectivity works -- names", {
-
-  kite <- graph_from_literal(
-    Andre - Beverly:Carol:Diane:Fernando,
-    Beverly - Andre:Diane:Ed:Garth,
-    Carol - Andre:Diane:Fernando,
-    Diane - Andre:Beverly:Carol:Ed:Fernando:Garth,
-    Ed - Beverly:Diane:Garth,
-    Fernando - Andre:Carol:Diane:Garth:Heather,
-    Garth - Beverly:Diane:Ed:Fernando:Heather,
-    Heather - Fernando:Garth:Ike,
-    Ike - Heather:Jane,
-    Jane - Ike
-  )
-
-  ec1 <- edge_connectivity(kite, source = "Heather", target = "Andre")
-  ec2 <- edge_connectivity(kite, source = "Garth", target = "Andre")
-  ec3 <- edge_connectivity(kite, source = "Garth", target = "Ike")
-  expect_equal(ec1, 2)
-  expect_equal(ec2, 4)
-  expect_equal(ec3, 1)
-})
diff --git a/tests/testthat/test-flow.R b/tests/testthat/test-flow.R
new file mode 100644
index 00000000000..cbc14307440
--- /dev/null
+++ b/tests/testthat/test-flow.R
@@ -0,0 +1,205 @@
+test_that("min_cut works -- value.only=FALSE", {
+  g_twosquares <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
+  E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
+  mc <- min_cut(g_twosquares, value.only = FALSE)
+
+  expect_equal(mc$value, 1)
+  expect_equal(as.vector(mc$cut), 2)
+  expect_equal(as.vector(mc$partition1), 2)
+  expect_equal(as.vector(mc$partition2), c(1, 3:6))
+})
+
+test_that("min_cut works -- value.only=TRUE", {
+  g_twosquares <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
+  E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
+  mc <- min_cut(g_twosquares, value.only = TRUE)
+
+  expect_equal(mc, 1)
+})
+
+test_that("min_cut works -- value.only=FALSE source/target", {
+  g_twosquares <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
+  E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
+  mc <- min_cut(g_twosquares, source = 1, target = 4, value.only = FALSE)
+
+  expect_equal(mc$value, 1)
+  expect_equal(as.vector(mc$cut), c(2, 5))
+  expect_equal(as.vector(mc$partition1), c(1, 2, 6))
+  expect_equal(as.vector(mc$partition2), c(3, 4, 5))
+})
+
+test_that("min_cut works -- value.only=TRUE", {
+  g_twosquares <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
+  E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
+  mc <- min_cut(g_twosquares, source = 1, target = 4, value.only = TRUE)
+
+  expect_equal(mc, 2)
+})
+
+
+test_that("min_cut errors work", {
+  g_ring <- make_ring(5, directed = TRUE, circular = TRUE)
+  E(g_ring)$capacity <- c(1, 2, 3, 4, 5)
+  expect_error(min_cut(g_ring, source = 1))
+  expect_error(min_cut(g_ring, target = 1))
+})
+
+test_that("st_cuts works", {
+  g_path <- graph_from_literal(a - +b - +c - +d - +e)
+  all_cuts_path <- st_cuts(g_path, source = "a", target = "e")
+  expect_equal(unvs(all_cuts_path$cuts), list(1, 2, 3, 4))
+  expect_equal(unvs(all_cuts_path$partition1s), list(1, 1:2, 1:3, 1:4))
+
+  g_star_v7 <- graph_from_literal(s - +a:b - +t, a - +1:2:3 - +b)
+  all_cuts_star_v7 <- st_cuts(g_star_v7, source = "s", target = "t")
+  expect_equal(unvs(all_cuts_star_v7$cuts), list(c(1, 2), c(1, 7), c(2, 3, 4, 5, 6), c(2, 3, 4, 5, 10), c(2, 3, 4, 6, 9), c(2, 3, 4, 9, 10), c(2, 3, 5, 6, 8), c(2, 3, 5, 8, 10), c(2, 3, 6, 8, 9), c(2, 3, 8, 9, 10), c(3, 7)))
+  expect_equal(
+    unvs(all_cuts_star_v7$partition1s),
+    list(1, c(1, 3), c(1, 2), c(1, 2, 7), c(1, 2, 6), c(1, 2, 6, 7), c(1, 2, 5), c(1, 2, 5, 7), c(1, 2, 5, 6), c(1, 2, 5, 6, 7), c(1, 2, 5, 6, 7, 3))
+  )
+
+  g_star_v9 <- graph_from_literal(s - +a:b - +t, a - +1:2:3:4:5 - +b)
+  all_cuts_star_v9 <- st_min_cuts(g_star_v9, source = "s", target = "t")
+  expect_equal(all_cuts_star_v9$value, 2)
+  expect_equal(unvs(all_cuts_star_v9$cuts), list(c(1, 2), c(1, 9), c(3, 9)))
+  expect_equal(unvs(all_cuts_star_v9$partition1s), list(1, c(1, 3), c(1, 3, 2, 9, 8, 7, 6, 5)))
+})
+
+test_that("max_flow works", {
+  edge_mat <- rbind(c(1, 3, 3), c(3, 4, 1), c(4, 2, 2), c(1, 5, 1), c(5, 6, 2), c(6, 2, 10))
+  colnames(edge_mat) <- c("from", "to", "capacity")
+  g_ring_acyc <- graph_from_data_frame(as.data.frame(edge_mat))
+  flow <- max_flow(g_ring_acyc, source = "1", target = "2")
+  expect_equal(flow$value, 2)
+  expect_equal(as.vector(flow$flow), rep(1, 6))
+  expect_equal(sort(as.vector(flow$cut)), c(2, 4))
+  expect_equal(sort(as.vector(flow$partition1)), 1:2)
+  expect_equal(sort(as.vector(flow$partition2)), 3:6)
+})
+
+test_that("vertex_connectivity works", {
+  g_path <- make_ring(5, circular = FALSE)
+  expect_equal(vertex_connectivity(g_path), 1)
+
+  g_disconnect <- make_graph(edges = c(1, 2, 3, 4), directed = FALSE)
+  expect_equal(vertex_connectivity(g_disconnect), 0)
+
+  g_ring <- make_ring(5, circular = TRUE)
+  expect_equal(vertex_connectivity(g_ring, source = 1, target = 4), 2)
+})
+
+test_that("edge_connectivity works", {
+  g_full <- make_full_graph(5)
+  expect_equal(edge_connectivity(g_full), 4)
+  expect_equal(edge_connectivity(g_full, source = 1, target = 2), 4)
+
+
+  g_path <- make_ring(5, directed = TRUE, circular = FALSE)
+  expect_equal(edge_connectivity(g_path), 0)
+  expect_equal(edge_connectivity(g_path, source = 1, target = 3), 1)
+})
+
+test_that("edge_connectivity works -- names", {
+  g_kite <- graph_from_literal(
+    Andre - Beverly:Carol:Diane:Fernando,
+    Beverly - Andre:Diane:Ed:Garth,
+    Carol - Andre:Diane:Fernando,
+    Diane - Andre:Beverly:Carol:Ed:Fernando:Garth,
+    Ed - Beverly:Diane:Garth,
+    Fernando - Andre:Carol:Diane:Garth:Heather,
+    Garth - Beverly:Diane:Ed:Fernando:Heather,
+    Heather - Fernando:Garth:Ike,
+    Ike - Heather:Jane,
+    Jane - Ike
+  )
+
+  ec1 <- edge_connectivity(g_kite, source = "Heather", target = "Andre")
+  expect_equal(ec1, 2)
+  ec2 <- edge_connectivity(g_kite, source = "Garth", target = "Andre")
+  expect_equal(ec2, 4)
+  ec3 <- edge_connectivity(g_kite, source = "Garth", target = "Ike")
+  expect_equal(ec3, 1)
+})
+
+test_that("dominator_tree works", {
+  g_tree <- graph_from_edgelist(matrix(c(1, 2, 2, 3, 3, 4, 2, 5, 5, 6), byrow = TRUE, ncol = 2), directed = TRUE)
+  dom_tree_tree <- dominator_tree(g_tree, 1)
+
+  expect_equal(dom_tree_tree$dom[2], 1)
+  expect_equal(dom_tree_tree$dom[3], 2)
+  expect_equal(dom_tree_tree$dom[5], 2)
+  expect_equal(dom_tree_tree$dom[6], 5)
+
+  g_one_vertex <- make_empty_graph(n = 1, directed = TRUE)
+  dom_tree_one <- dominator_tree(g_one_vertex, 1)
+
+  expect_equal(dom_tree_one$dom[1], -1)
+})
+
+test_that("dominator_tree errors work", {
+  g_tree <- graph_from_edgelist(matrix(c(1, 2, 2, 3, 3, 4, 2, 5, 5, 6), byrow = TRUE, ncol = 2), directed = TRUE)
+  expect_error(dominator_tree(g_tree))
+})
+
+test_that("dominator_tree works -- legacy", {
+  g <- graph_from_literal(
+    R - +A:B:C, A - +D, B - +A:D:E, C - +F:G, D - +L,
+    E - +H, F - +I, G - +I:J, H - +E:K, I - +K, J - +I,
+    K - +I:R, L - +H
+  )
+  dtree <- dominator_tree(g, root = "R")
+  names <- c("$root", V(g)$name)
+  dtree$dom <- names[ifelse(dtree$dom < 0, 1, dtree$dom + 1)]
+  dtree$leftout <- V(g)$name[dtree$leftout]
+  expect_equal(dtree$dom, c("$root", "R", "R", "R", "R", "R", "C", "C", "D", "R", "R", "G", "R"))
+  expect_equal(dtree$leftout, character())
+  expect_equal(
+    as_edgelist(dtree$domtree),
+    structure(c("R", "R", "R", "R", "R", "C", "C", "D", "R", "R", "G", "R", "A", "B", "C", "D", "E", "F", "G", "L", "H", "I", "J", "K"), .Dim = c(12L, 2L))
+  )
+})
+
+test_that("min_st_separators works", {
+  g_zachary <- make_graph("Zachary")
+  msts <- min_st_separators(g_zachary)
+  is <- sapply(msts, is_separator, graph = g_zachary)
+  expect_equal(unique(is), TRUE)
+
+  ## TODO: check that it is minimal
+})
+
+test_that("min_st_separators() works for the note case", {
+  g_note <- make_graph(~ 0 - 1 - 2 - 3 - 4 - 1)
+  expect_snapshot(
+    min_st_separators(g_note),
+    transform = function(x) gsub("from.*", "from something", x)
+  )
+})
+
+test_that("Minimal s-t separators work", {
+  # bug 1033045
+  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))
+})
+
+test_that("min_separators works", {
+  camp <- graph_from_literal(
+    Harry:Steve:Don:Bert - Harry:Steve:Don:Bert,
+    Pam:Brazey:Carol:Pat - Pam:Brazey:Carol:Pat,
+    Holly - Carol:Pat:Pam:Jennie:Bill,
+    Bill - Pauline:Michael:Lee:Holly,
+    Pauline - Bill:Jennie:Ann,
+    Jennie - Holly:Michael:Lee:Ann:Pauline,
+    Michael - Bill:Jennie:Ann:Lee:John,
+    Ann - Michael:Jennie:Pauline,
+    Lee - Michael:Bill:Jennie,
+    Gery - Pat:Steve:Russ:John,
+    Russ - Steve:Bert:Gery:John,
+    John - Gery:Russ:Michael
+  )
+  camp <- simplify(camp)
+  sep <- min_separators(camp)
+  expect_true(all(sapply(sep, is_min_separator, graph = camp)))
+})
diff --git a/tests/testthat/test-graph.maxflow.R b/tests/testthat/test-graph.maxflow.R
deleted file mode 100644
index c8849665a7a..00000000000
--- a/tests/testthat/test-graph.maxflow.R
+++ /dev/null
@@ -1,11 +0,0 @@
-test_that("max_flow works", {
-  E <- rbind(c(1, 3, 3), c(3, 4, 1), c(4, 2, 2), c(1, 5, 1), c(5, 6, 2), c(6, 2, 10))
-  colnames(E) <- c("from", "to", "capacity")
-  g1 <- graph_from_data_frame(as.data.frame(E))
-  fl <- max_flow(g1, source = "1", target = "2")
-  expect_equal(fl$value, 2)
-  expect_equal(as.vector(fl$flow), rep(1, 6))
-  expect_equal(sort(as.vector(fl$cut)), c(2, 4))
-  expect_equal(sort(as.vector(fl$partition1)), 1:2)
-  expect_equal(sort(as.vector(fl$partition2)), 3:6)
-})
diff --git a/tests/testthat/test-graph.mincut.R b/tests/testthat/test-graph.mincut.R
deleted file mode 100644
index 18066226b03..00000000000
--- a/tests/testthat/test-graph.mincut.R
+++ /dev/null
@@ -1,21 +0,0 @@
-test_that("min_cut works", {
-  g2 <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
-  E(g2)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
-  mc <- min_cut(g2, value.only = FALSE)
-
-  expect_equal(mc$value, 1)
-  expect_equal(as.vector(mc$cut), 2)
-  expect_equal(as.vector(mc$partition1), 2)
-  expect_equal(as.vector(mc$partition2), c(1, 3:6))
-})
-
-test_that("s-t min_cut works", {
-  g2 <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
-  E(g2)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
-  mc <- min_cut(g2, source = 2, target = 4, value.only = FALSE)
-
-  expect_equal(mc$value, 1)
-  expect_equal(as.vector(mc$cut), 2)
-  expect_equal(as.vector(mc$partition1), 2)
-  expect_equal(as.vector(mc$partition2), c(1, 3:6))
-})
diff --git a/tests/testthat/test-minimal.st.separators.R b/tests/testthat/test-minimal.st.separators.R
deleted file mode 100644
index 7da2118492c..00000000000
--- a/tests/testthat/test-minimal.st.separators.R
+++ /dev/null
@@ -1,16 +0,0 @@
-test_that("min_st_separators works", {
-  g <- make_graph("Zachary")
-  msts <- min_st_separators(g)
-  is <- sapply(msts, is_separator, graph = g)
-  expect_equal(unique(is), TRUE)
-
-  ## TODO: check that it is minimal
-})
-
-test_that("min_st_separators() works for the note case", {
-  g <- make_graph(~ 0 - 1 - 2 - 3 - 4 - 1)
-  expect_snapshot(
-    min_st_separators(g),
-    transform = function(x) gsub("from.*", "from something", x)
-  )
-})
diff --git a/tests/testthat/test-minimum.size.separators.R b/tests/testthat/test-minimum.size.separators.R
deleted file mode 100644
index 92563101579..00000000000
--- a/tests/testthat/test-minimum.size.separators.R
+++ /dev/null
@@ -1,19 +0,0 @@
-test_that("min_separators works", {
-  camp <- graph_from_literal(
-    Harry:Steve:Don:Bert - Harry:Steve:Don:Bert,
-    Pam:Brazey:Carol:Pat - Pam:Brazey:Carol:Pat,
-    Holly - Carol:Pat:Pam:Jennie:Bill,
-    Bill - Pauline:Michael:Lee:Holly,
-    Pauline - Bill:Jennie:Ann,
-    Jennie - Holly:Michael:Lee:Ann:Pauline,
-    Michael - Bill:Jennie:Ann:Lee:John,
-    Ann - Michael:Jennie:Pauline,
-    Lee - Michael:Bill:Jennie,
-    Gery - Pat:Steve:Russ:John,
-    Russ - Steve:Bert:Gery:John,
-    John - Gery:Russ:Michael
-  )
-  camp <- simplify(camp)
-  sep <- min_separators(camp)
-  expect_true(all(sapply(sep, is_min_separator, graph = camp)))
-})

From 76dcbdd1a73f3c1b36dfd897c5acc9a187fb49c9 Mon Sep 17 00:00:00 2001
From: schochastics <david@schochastics.net>
Date: Mon, 10 Feb 2025 05:25:55 +0100
Subject: [PATCH 2/8] fixed failing tests

---
 tests/testthat/_snaps/flow.md | 2 +-
 tests/testthat/test-flow.R    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/testthat/_snaps/flow.md b/tests/testthat/_snaps/flow.md
index 7add2e27c28..539aebf30bc 100644
--- a/tests/testthat/_snaps/flow.md
+++ b/tests/testthat/_snaps/flow.md
@@ -1,7 +1,7 @@
 # min_st_separators() works for the note case
 
     Code
-      min_st_separators(g)
+      min_st_separators(g_note)
     Output
       [[1]]
       + 1/5 vertex, named, from something
diff --git a/tests/testthat/test-flow.R b/tests/testthat/test-flow.R
index cbc14307440..eb0b31fbca4 100644
--- a/tests/testthat/test-flow.R
+++ b/tests/testthat/test-flow.R
@@ -22,7 +22,7 @@ test_that("min_cut works -- value.only=FALSE source/target", {
   E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
   mc <- min_cut(g_twosquares, source = 1, target = 4, value.only = FALSE)
 
-  expect_equal(mc$value, 1)
+  expect_equal(mc$value, 2)
   expect_equal(as.vector(mc$cut), c(2, 5))
   expect_equal(as.vector(mc$partition1), c(1, 2, 6))
   expect_equal(as.vector(mc$partition2), c(3, 4, 5))

From 3bf022a98cf3212d0fe08717e1971939e7aa7e11 Mon Sep 17 00:00:00 2001
From: schochastics <david@schochastics.net>
Date: Mon, 10 Feb 2025 06:03:31 +0100
Subject: [PATCH 3/8] added more error tests

---
 R/flow.R                   |  2 +-
 tests/testthat/test-flow.R | 59 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/R/flow.R b/R/flow.R
index 1fb693b503e..98ef822d88f 100644
--- a/R/flow.R
+++ b/R/flow.R
@@ -433,7 +433,7 @@ vertex_connectivity <- function(graph, source = NULL, target = NULL, checks = TR
       as_igraph_vs(graph, target) - 1
     )
   } else {
-    stop("either give both source and target or neither")
+    cli::cli_abort("Either give both source and target or neither")
   }
 }
 
diff --git a/tests/testthat/test-flow.R b/tests/testthat/test-flow.R
index eb0b31fbca4..75523512a7d 100644
--- a/tests/testthat/test-flow.R
+++ b/tests/testthat/test-flow.R
@@ -65,6 +65,14 @@ test_that("st_cuts works", {
   expect_equal(unvs(all_cuts_star_v9$partition1s), list(1, c(1, 3), c(1, 3, 2, 9, 8, 7, 6, 5)))
 })
 
+test_that("st_cuts errors work", {
+  g_path <- graph_from_literal(a - +b - +c - +d - +e)
+  expect_error(st_cuts(g_path, source = "a", target = NULL))
+  expect_error(st_cuts(g_path, source = NULL, target = "a"))
+  expect_error(st_min_cuts(g_path, source = "a", target = NULL))
+  expect_error(st_min_cuts(g_path, source = NULL, target = "a"))
+})
+
 test_that("max_flow works", {
   edge_mat <- rbind(c(1, 3, 3), c(3, 4, 1), c(4, 2, 2), c(1, 5, 1), c(5, 6, 2), c(6, 2, 10))
   colnames(edge_mat) <- c("from", "to", "capacity")
@@ -88,6 +96,11 @@ test_that("vertex_connectivity works", {
   expect_equal(vertex_connectivity(g_ring, source = 1, target = 4), 2)
 })
 
+test_that("vertex_connectivity error works", {
+  g_path <- make_ring(5, circular = FALSE)
+  expect_error(vertex_connectivity(g_path, source = 1))
+})
+
 test_that("edge_connectivity works", {
   g_full <- make_full_graph(5)
   expect_equal(edge_connectivity(g_full), 4)
@@ -121,6 +134,51 @@ test_that("edge_connectivity works -- names", {
   expect_equal(ec3, 1)
 })
 
+test_that("edge_connectivity error works", {
+  g_path <- make_ring(5, circular = FALSE)
+  expect_error(edge_connectivity(g_path, source = 1))
+})
+
+test_that("edge_disjoint_paths works", {
+  g_full <- make_full_graph(5)
+  expect_equal(edge_disjoint_paths(g_full, source = 1, target = 2), 4)
+
+  g_path <- make_ring(5, directed = TRUE, circular = FALSE)
+  expect_equal(edge_disjoint_paths(g_path, source = 1, target = 3), 1)
+})
+
+test_that("edge_disjoint_paths error works", {
+  g_path <- make_ring(5, circular = FALSE)
+  expect_error(edge_disjoint_paths(g_path, source = 1))
+})
+
+test_that("vertex_disjoint_paths works", {
+  g_full <- make_full_graph(5)
+  expect_equal(vertex_disjoint_paths(g_full, source = 1, target = 2), 4)
+
+  g_path <- make_ring(5, directed = TRUE, circular = FALSE)
+  expect_equal(vertex_disjoint_paths(g_path, source = 1, target = 3), 1)
+})
+
+test_that("vertex_disjoint_paths error works", {
+  g_path <- make_ring(5, circular = FALSE)
+  expect_error(vertex_disjoint_paths(g_path, source = 1))
+})
+
+test_that("adhesion works", {
+  g_full <- make_full_graph(5)
+  expect_equal(adhesion(g_full), 4)
+
+  g_path <- make_ring(5, directed = TRUE, circular = FALSE)
+  expect_equal(adhesion(g_path), 0)
+})
+
+test_that("vertex_disjoint_paths error works", {
+  g_path <- make_ring(5, circular = FALSE)
+  expect_error(vertex_disjoint_paths(g_path, source = 1))
+})
+
+
 test_that("dominator_tree works", {
   g_tree <- graph_from_edgelist(matrix(c(1, 2, 2, 3, 3, 4, 2, 5, 5, 6), byrow = TRUE, ncol = 2), directed = TRUE)
   dom_tree_tree <- dominator_tree(g_tree, 1)
@@ -139,6 +197,7 @@ test_that("dominator_tree works", {
 test_that("dominator_tree errors work", {
   g_tree <- graph_from_edgelist(matrix(c(1, 2, 2, 3, 3, 4, 2, 5, 5, 6), byrow = TRUE, ncol = 2), directed = TRUE)
   expect_error(dominator_tree(g_tree))
+  expect_error(dominator_tree(g_tree, root = NULL))
 })
 
 test_that("dominator_tree works -- legacy", {

From ba7393859e977cce7816506a3d690ab05cf0ff30 Mon Sep 17 00:00:00 2001
From: schochastics <david@schochastics.net>
Date: Mon, 10 Feb 2025 10:34:51 +0100
Subject: [PATCH 4/8] added better R error handling

---
 R/flow.R                   | 7 ++++++-
 tests/testthat/test-flow.R | 3 ++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/R/flow.R b/R/flow.R
index 98ef822d88f..09c344f2c6c 100644
--- a/R/flow.R
+++ b/R/flow.R
@@ -538,7 +538,9 @@ edge_connectivity <- function(graph, source = NULL, target = NULL, checks = TRUE
 #' @export
 edge_disjoint_paths <- function(graph, source = NULL, target = NULL) {
   ensure_igraph(graph)
-
+  if (is.null(source) || is.null(target)) {
+    cli::cli_abort("Both source and target must be given")
+  }
   on.exit(.Call(R_igraph_finalizer))
   .Call(
     R_igraph_edge_disjoint_paths, graph,
@@ -550,6 +552,9 @@ edge_disjoint_paths <- function(graph, source = NULL, target = NULL) {
 #' @export
 vertex_disjoint_paths <- function(graph, source = NULL, target = NULL) {
   ensure_igraph(graph)
+  if (is.null(source) || is.null(target)) {
+    cli::cli_abort("Both source and target must be given")
+  }
 
   on.exit(.Call(R_igraph_finalizer))
   .Call(
diff --git a/tests/testthat/test-flow.R b/tests/testthat/test-flow.R
index 75523512a7d..cfcb8cdcdba 100644
--- a/tests/testthat/test-flow.R
+++ b/tests/testthat/test-flow.R
@@ -149,7 +149,8 @@ test_that("edge_disjoint_paths works", {
 
 test_that("edge_disjoint_paths error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_error(edge_disjoint_paths(g_path, source = 1))
+  expect_error(edge_disjoint_paths(g_path, source = 1, target = NULL))
+  expect_error(edge_disjoint_paths(g_path, source = NULL, target = 1))
 })
 
 test_that("vertex_disjoint_paths works", {

From b11a3c96c90a68793aeb8543bb2af4df5ff95838 Mon Sep 17 00:00:00 2001
From: David Schoch <david@schochastics.net>
Date: Thu, 13 Feb 2025 18:49:54 +0100
Subject: [PATCH 5/8] fixed cli calls
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Maëlle Salmon <maelle.salmon@yahoo.se>
---
 R/flow.R | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/R/flow.R b/R/flow.R
index 09c344f2c6c..8a852f0f583 100644
--- a/R/flow.R
+++ b/R/flow.R
@@ -291,7 +291,10 @@ min_cut <- function(graph, source = NULL, target = NULL, capacity = NULL, value.
   }
 
   if (xor(is.null(source), is.null(target))) {
-    cli::cli_abort("Please give both source and target or neither")
+    cli::cli_abort(c(
+      "{.arg source} and {.arg target} must not be specified at the same time.",
+      i = "Specify either {.arg source} or {.arg target} or neither."
+    ))
   }
 
   if (!is.null(capacity)) {
@@ -433,7 +436,10 @@ vertex_connectivity <- function(graph, source = NULL, target = NULL, checks = TR
       as_igraph_vs(graph, target) - 1
     )
   } else {
-    cli::cli_abort("Either give both source and target or neither")
+    cli::cli_abort(c(
+      "{.arg source} and {.arg target} must not be specified at the same time.",
+      i = "Specify either {.arg source} or {.arg target} or neither."
+    ))
   }
 }
 
@@ -530,7 +536,10 @@ edge_connectivity <- function(graph, source = NULL, target = NULL, checks = TRUE
       as_igraph_vs(graph, source) - 1, as_igraph_vs(graph, target) - 1
     )
   } else {
-    cli::cli_abort("Either give both source and target or neither")
+    cli::cli_abort(c(
+      "{.arg source} and {.arg target} must not be specified at the same time.",
+      i = "Specify either {.arg source} or {.arg target} or neither."
+    ))
   }
 }
 
@@ -731,7 +740,7 @@ dominator_tree <- function(graph, root, mode = c("out", "in", "all", "total")) {
   ensure_igraph(graph)
   root <- as_igraph_vs(graph, root)
   if (length(root) == 0) {
-    cli::cli_abort("No vertex was specified")
+    cli::cli_abort("{.arg root} must be specified.")
   }
   mode <- switch(igraph.match.arg(mode),
     "out" = 1,

From f3ab2c5adf95957cfaa0eee4255b8eb8390bc00d Mon Sep 17 00:00:00 2001
From: David Schoch <david@schochastics.net>
Date: Thu, 13 Feb 2025 19:11:31 +0100
Subject: [PATCH 6/8] fixed test names
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Maëlle Salmon <maelle.salmon@yahoo.se>
---
 tests/testthat/test-flow.R | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/tests/testthat/test-flow.R b/tests/testthat/test-flow.R
index cfcb8cdcdba..9e1fcd4bbe4 100644
--- a/tests/testthat/test-flow.R
+++ b/tests/testthat/test-flow.R
@@ -1,4 +1,4 @@
-test_that("min_cut works -- value.only=FALSE", {
+test_that("min_cut() works -- value.only=FALSE", {
   g_twosquares <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
   E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
   mc <- min_cut(g_twosquares, value.only = FALSE)
@@ -9,7 +9,7 @@ test_that("min_cut works -- value.only=FALSE", {
   expect_equal(as.vector(mc$partition2), c(1, 3:6))
 })
 
-test_that("min_cut works -- value.only=TRUE", {
+test_that("min_cut() works -- value.only=TRUE", {
   g_twosquares <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
   E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
   mc <- min_cut(g_twosquares, value.only = TRUE)
@@ -17,7 +17,7 @@ test_that("min_cut works -- value.only=TRUE", {
   expect_equal(mc, 1)
 })
 
-test_that("min_cut works -- value.only=FALSE source/target", {
+test_that("min_cut() works -- value.only=FALSE source/target", {
   g_twosquares <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
   E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
   mc <- min_cut(g_twosquares, source = 1, target = 4, value.only = FALSE)
@@ -28,7 +28,7 @@ test_that("min_cut works -- value.only=FALSE source/target", {
   expect_equal(as.vector(mc$partition2), c(3, 4, 5))
 })
 
-test_that("min_cut works -- value.only=TRUE", {
+test_that("min_cut() works -- value.only=TRUE", {
   g_twosquares <- make_graph(c(1, 2, 2, 3, 3, 4, 1, 6, 6, 5, 5, 4, 4, 1))
   E(g_twosquares)$capacity <- c(3, 1, 2, 10, 1, 3, 2)
   mc <- min_cut(g_twosquares, source = 1, target = 4, value.only = TRUE)
@@ -37,14 +37,14 @@ test_that("min_cut works -- value.only=TRUE", {
 })
 
 
-test_that("min_cut errors work", {
+test_that("min_cut() errors work", {
   g_ring <- make_ring(5, directed = TRUE, circular = TRUE)
   E(g_ring)$capacity <- c(1, 2, 3, 4, 5)
   expect_error(min_cut(g_ring, source = 1))
   expect_error(min_cut(g_ring, target = 1))
 })
 
-test_that("st_cuts works", {
+test_that("st_cuts() works", {
   g_path <- graph_from_literal(a - +b - +c - +d - +e)
   all_cuts_path <- st_cuts(g_path, source = "a", target = "e")
   expect_equal(unvs(all_cuts_path$cuts), list(1, 2, 3, 4))
@@ -80,12 +80,12 @@ test_that("max_flow works", {
   flow <- max_flow(g_ring_acyc, source = "1", target = "2")
   expect_equal(flow$value, 2)
   expect_equal(as.vector(flow$flow), rep(1, 6))
-  expect_equal(sort(as.vector(flow$cut)), c(2, 4))
-  expect_equal(sort(as.vector(flow$partition1)), 1:2)
-  expect_equal(sort(as.vector(flow$partition2)), 3:6)
+  expect_setequal(as.vector(flow$cut), c(2, 4))
+  expect_setequal(as.vector(flow$partition1), 1:2)
+  expect_setequal(as.vector(flow$partition2), 3:6)
 })
 
-test_that("vertex_connectivity works", {
+test_that("vertex_connectivity() works", {
   g_path <- make_ring(5, circular = FALSE)
   expect_equal(vertex_connectivity(g_path), 1)
 

From ce6cb74e01853e87a5e4e883de4b5820e2fe56b0 Mon Sep 17 00:00:00 2001
From: schochastics <david@schochastics.net>
Date: Thu, 13 Feb 2025 19:40:39 +0100
Subject: [PATCH 7/8] converted error tests to snapshot tests

---
 tests/testthat/_snaps/flow.md | 98 +++++++++++++++++++++++++++++++++++
 tests/testthat/test-flow.R    | 40 +++++++++-----
 2 files changed, 124 insertions(+), 14 deletions(-)

diff --git a/tests/testthat/_snaps/flow.md b/tests/testthat/_snaps/flow.md
index 539aebf30bc..bf24e513c67 100644
--- a/tests/testthat/_snaps/flow.md
+++ b/tests/testthat/_snaps/flow.md
@@ -1,3 +1,101 @@
+# st_cuts errors work
+
+    Code
+      st_cuts(g_path, source = "a", target = NULL)
+    Condition
+      Error in `st_cuts()`:
+      ! No vertex was specified
+
+---
+
+    Code
+      st_cuts(g_path, source = NULL, target = "a")
+    Condition
+      Error in `st_cuts()`:
+      ! No vertex was specified
+
+---
+
+    Code
+      st_min_cuts(g_path, source = "a", target = NULL)
+    Condition
+      Error in `st_min_cuts()`:
+      ! No vertex was specified
+
+---
+
+    Code
+      st_min_cuts(g_path, source = NULL, target = "a")
+    Condition
+      Error in `st_min_cuts()`:
+      ! No vertex was specified
+
+# vertex_connectivity error works
+
+    Code
+      vertex_connectivity(g_path, source = 1)
+    Condition
+      Error in `vertex_connectivity()`:
+      ! `source` and `target` must not be specified at the same time.
+      i Specify either `source` or `target` or neither.
+
+# edge_connectivity error works
+
+    Code
+      edge_connectivity(g_path, source = 1)
+    Condition
+      Error in `edge_connectivity()`:
+      ! `source` and `target` must not be specified at the same time.
+      i Specify either `source` or `target` or neither.
+
+# edge_disjoint_paths error works
+
+    Code
+      edge_disjoint_paths(g_path, source = 1, target = NULL)
+    Condition
+      Error in `edge_disjoint_paths()`:
+      ! Both source and target must be given
+
+---
+
+    Code
+      edge_disjoint_paths(g_path, source = NULL, target = 1)
+    Condition
+      Error in `edge_disjoint_paths()`:
+      ! Both source and target must be given
+
+# vertex_disjoint_paths error works
+
+    Code
+      vertex_disjoint_paths(g_path, source = 1)
+    Condition
+      Error in `vertex_disjoint_paths()`:
+      ! Both source and target must be given
+
+---
+
+    Code
+      vertex_disjoint_paths(g_path, source = 1)
+    Condition
+      Error in `vertex_disjoint_paths()`:
+      ! Both source and target must be given
+
+# dominator_tree errors work
+
+    Code
+      dominator_tree(g_tree)
+    Condition
+      Error in `dominator_tree()`:
+      ! argument "root" is missing, with no default
+
+---
+
+    Code
+      dominator_tree(g_tree, root = NULL)
+    Condition
+      Error in `dominator_tree()`:
+      ! `root` must be specified.
+
 # min_st_separators() works for the note case
 
     Code
diff --git a/tests/testthat/test-flow.R b/tests/testthat/test-flow.R
index 9e1fcd4bbe4..655b6a33fb0 100644
--- a/tests/testthat/test-flow.R
+++ b/tests/testthat/test-flow.R
@@ -52,10 +52,21 @@ test_that("st_cuts() works", {
 
   g_star_v7 <- graph_from_literal(s - +a:b - +t, a - +1:2:3 - +b)
   all_cuts_star_v7 <- st_cuts(g_star_v7, source = "s", target = "t")
-  expect_equal(unvs(all_cuts_star_v7$cuts), list(c(1, 2), c(1, 7), c(2, 3, 4, 5, 6), c(2, 3, 4, 5, 10), c(2, 3, 4, 6, 9), c(2, 3, 4, 9, 10), c(2, 3, 5, 6, 8), c(2, 3, 5, 8, 10), c(2, 3, 6, 8, 9), c(2, 3, 8, 9, 10), c(3, 7)))
+  expect_equal(
+    unvs(all_cuts_star_v7$cuts),
+    list(
+      c(1, 2), c(1, 7), c(2, 3, 4, 5, 6), c(2, 3, 4, 5, 10),
+      c(2, 3, 4, 6, 9), c(2, 3, 4, 9, 10), c(2, 3, 5, 6, 8),
+      c(2, 3, 5, 8, 10), c(2, 3, 6, 8, 9), c(2, 3, 8, 9, 10), c(3, 7)
+    )
+  )
   expect_equal(
     unvs(all_cuts_star_v7$partition1s),
-    list(1, c(1, 3), c(1, 2), c(1, 2, 7), c(1, 2, 6), c(1, 2, 6, 7), c(1, 2, 5), c(1, 2, 5, 7), c(1, 2, 5, 6), c(1, 2, 5, 6, 7), c(1, 2, 5, 6, 7, 3))
+    list(
+      1, c(1, 3), c(1, 2), c(1, 2, 7), c(1, 2, 6),
+      c(1, 2, 6, 7), c(1, 2, 5), c(1, 2, 5, 7),
+      c(1, 2, 5, 6), c(1, 2, 5, 6, 7), c(1, 2, 5, 6, 7, 3)
+    )
   )
 
   g_star_v9 <- graph_from_literal(s - +a:b - +t, a - +1:2:3:4:5 - +b)
@@ -67,10 +78,11 @@ test_that("st_cuts() works", {
 
 test_that("st_cuts errors work", {
   g_path <- graph_from_literal(a - +b - +c - +d - +e)
-  expect_error(st_cuts(g_path, source = "a", target = NULL))
-  expect_error(st_cuts(g_path, source = NULL, target = "a"))
-  expect_error(st_min_cuts(g_path, source = "a", target = NULL))
-  expect_error(st_min_cuts(g_path, source = NULL, target = "a"))
+
+  expect_snapshot(st_cuts(g_path, source = "a", target = NULL), error = TRUE)
+  expect_snapshot(st_cuts(g_path, source = NULL, target = "a"), error = TRUE)
+  expect_snapshot(st_min_cuts(g_path, source = "a", target = NULL), error = TRUE)
+  expect_snapshot(st_min_cuts(g_path, source = NULL, target = "a"), error = TRUE)
 })
 
 test_that("max_flow works", {
@@ -98,7 +110,7 @@ test_that("vertex_connectivity() works", {
 
 test_that("vertex_connectivity error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_error(vertex_connectivity(g_path, source = 1))
+  expect_snapshot(vertex_connectivity(g_path, source = 1), error = TRUE)
 })
 
 test_that("edge_connectivity works", {
@@ -136,7 +148,7 @@ test_that("edge_connectivity works -- names", {
 
 test_that("edge_connectivity error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_error(edge_connectivity(g_path, source = 1))
+  expect_snapshot(edge_connectivity(g_path, source = 1), error = TRUE)
 })
 
 test_that("edge_disjoint_paths works", {
@@ -149,8 +161,8 @@ test_that("edge_disjoint_paths works", {
 
 test_that("edge_disjoint_paths error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_error(edge_disjoint_paths(g_path, source = 1, target = NULL))
-  expect_error(edge_disjoint_paths(g_path, source = NULL, target = 1))
+  expect_snapshot(edge_disjoint_paths(g_path, source = 1, target = NULL), error = TRUE)
+  expect_snapshot(edge_disjoint_paths(g_path, source = NULL, target = 1), error = TRUE)
 })
 
 test_that("vertex_disjoint_paths works", {
@@ -163,7 +175,7 @@ test_that("vertex_disjoint_paths works", {
 
 test_that("vertex_disjoint_paths error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_error(vertex_disjoint_paths(g_path, source = 1))
+  expect_snapshot(vertex_disjoint_paths(g_path, source = 1), error = TRUE)
 })
 
 test_that("adhesion works", {
@@ -176,7 +188,7 @@ test_that("adhesion works", {
 
 test_that("vertex_disjoint_paths error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_error(vertex_disjoint_paths(g_path, source = 1))
+  expect_snapshot(vertex_disjoint_paths(g_path, source = 1), error = TRUE)
 })
 
 
@@ -197,8 +209,8 @@ test_that("dominator_tree works", {
 
 test_that("dominator_tree errors work", {
   g_tree <- graph_from_edgelist(matrix(c(1, 2, 2, 3, 3, 4, 2, 5, 5, 6), byrow = TRUE, ncol = 2), directed = TRUE)
-  expect_error(dominator_tree(g_tree))
-  expect_error(dominator_tree(g_tree, root = NULL))
+  expect_snapshot(dominator_tree(g_tree), error = TRUE)
+  expect_snapshot(dominator_tree(g_tree, root = NULL), error = TRUE)
 })
 
 test_that("dominator_tree works -- legacy", {

From 3dedcabb7f1fb5be309ecb70c6728ab1ca130be5 Mon Sep 17 00:00:00 2001
From: schochastics <david@schochastics.net>
Date: Thu, 13 Feb 2025 20:51:19 +0100
Subject: [PATCH 8/8] fixed dominator_tree tests

---
 R/flow.R                      | 6 ++++--
 tests/testthat/_snaps/flow.md | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/R/flow.R b/R/flow.R
index 8a852f0f583..46ba4993642 100644
--- a/R/flow.R
+++ b/R/flow.R
@@ -738,10 +738,12 @@ st_min_cuts <- all_st_mincuts_impl
 dominator_tree <- function(graph, root, mode = c("out", "in", "all", "total")) {
   # Argument checks
   ensure_igraph(graph)
-  root <- as_igraph_vs(graph, root)
-  if (length(root) == 0) {
+
+  if (missing(root) || is.null(root)) {
     cli::cli_abort("{.arg root} must be specified.")
   }
+  root <- as_igraph_vs(graph, root)
+
   mode <- switch(igraph.match.arg(mode),
     "out" = 1,
     "in" = 2,
diff --git a/tests/testthat/_snaps/flow.md b/tests/testthat/_snaps/flow.md
index bf24e513c67..01e1e52f55a 100644
--- a/tests/testthat/_snaps/flow.md
+++ b/tests/testthat/_snaps/flow.md
@@ -86,7 +86,7 @@
       dominator_tree(g_tree)
     Condition
       Error in `dominator_tree()`:
-      ! argument "root" is missing, with no default
+      ! `root` must be specified.
 
 ---