From b6e0492593a6c6e30f7a1292949e0fffda6fe717 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 24 Jan 2026 09:48:18 +0000
Subject: [PATCH 1/5] Initial plan


From ca6e52d330c8ee439a49dd9a0ff112a7732a0dcf Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 24 Jan 2026 09:58:32 +0000
Subject: [PATCH 2/5] refactor: use expect_snapshot_igraph_error() and move
 test function to separate file

Co-authored-by: krlmlr <1741643+krlmlr@users.noreply.github.com>
---
 src/rinterface_extra.c                      |  7 -----
 src/test_error_with_source.c                | 33 +++++++++++++++++++++
 tests/testthat/test-adjacency.R             |  2 +-
 tests/testthat/test-attributes.R            | 18 +++++------
 tests/testthat/test-centrality.R            |  2 +-
 tests/testthat/test-conversion.R            |  6 ++--
 tests/testthat/test-error-formatting.R      |  4 +++
 tests/testthat/test-fit.R                   |  2 +-
 tests/testthat/test-flow.R                  | 16 +++++-----
 tests/testthat/test-foreign.R               |  8 ++---
 tests/testthat/test-hrg.R                   |  4 +--
 tests/testthat/test-incidence.R             |  8 ++---
 tests/testthat/test-interface.R             |  6 ++--
 tests/testthat/test-iterators.R             |  4 +--
 tests/testthat/test-layout.R                |  6 ++--
 tests/testthat/test-make.R                  |  6 ++--
 tests/testthat/test-other.R                 |  2 +-
 tests/testthat/test-plot.R                  |  2 +-
 tests/testthat/test-structural-properties.R |  4 +--
 tests/testthat/test-versions.R              | 18 +++++------
 20 files changed, 94 insertions(+), 64 deletions(-)
 create mode 100644 src/test_error_with_source.c

diff --git a/src/rinterface_extra.c b/src/rinterface_extra.c
index d88ba20810e..9e8c68c9332 100644
--- a/src/rinterface_extra.c
+++ b/src/rinterface_extra.c
@@ -7760,13 +7760,6 @@ SEXP Rx_igraph_create_bipartite(SEXP types, SEXP edges, SEXP directed) {
   return R_igraph_create_bipartite(types, edges, directed);
 }
 
-/* Test function to verify error formatting with file and line information */
-attribute_visible SEXP Rx_igraph_test_error_with_source(void) {
-  igraph_errorf("Test error message for verifying source location formatting",
-                __FILE__, __LINE__, IGRAPH_EINVAL);
-  return R_NilValue;
-}
-
 SEXP Rx_igraph_finalizer(void) {
   return R_igraph_finalizer();
 }
diff --git a/src/test_error_with_source.c b/src/test_error_with_source.c
new file mode 100644
index 00000000000..3a66e48ba34
--- /dev/null
+++ b/src/test_error_with_source.c
@@ -0,0 +1,33 @@
+/* -*- mode: C -*-  */
+/*
+   IGraph library R interface.
+   Copyright (C) 2013  Gabor Csardi <csardi.gabor@gmail.com>
+   334 Harvard street, Cambridge, MA 02139 USA
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+   02110-1301 USA
+
+*/
+
+#include "rinterface.h"
+
+#include <R_ext/Visibility.h>
+
+/* Test function to verify error formatting with file and line information */
+attribute_visible SEXP Rx_igraph_test_error_with_source(void) {
+  igraph_errorf("Test error message for verifying source location formatting",
+                __FILE__, __LINE__, IGRAPH_EINVAL);
+  return R_NilValue;
+}
diff --git a/tests/testthat/test-adjacency.R b/tests/testthat/test-adjacency.R
index b488ca4302d..cd8c838e468 100644
--- a/tests/testthat/test-adjacency.R
+++ b/tests/testthat/test-adjacency.R
@@ -787,7 +787,7 @@ test_that("sparse/dense matrices min/max/plus", {
 
 test_that("graph_from_adjacency_matrix errors for NAs", {
   A <- matrix(c(1, 1, NA, 1), 2, 2)
-  expect_snapshot(graph_from_adjacency_matrix(A), error = TRUE)
+  expect_snapshot_igraph_error(graph_from_adjacency_matrix(A))
 })
 
 test_that("graph_from_adjacency_matrix handles add.colnames and add.rownames = FALSE correctly", {
diff --git a/tests/testthat/test-attributes.R b/tests/testthat/test-attributes.R
index 71d70df15f8..bf54e2ae311 100644
--- a/tests/testthat/test-attributes.R
+++ b/tests/testthat/test-attributes.R
@@ -436,13 +436,13 @@ test_that("adding and removing attributes", {
 
 test_that("error messages work", {
   g <- make_full_graph(5)
-  expect_snapshot(set_vertex_attr(g, "test", value = c(1, 2)), error = TRUE)
-  expect_snapshot(set_edge_attr(g, "test", value = c(1, 2)), error = TRUE)
-  expect_snapshot(delete_graph_attr(g, "a"), error = TRUE)
-  expect_snapshot(delete_vertex_attr(g, "a"), error = TRUE)
-  expect_snapshot(delete_edge_attr(g, "a"), error = TRUE)
-  expect_snapshot(assert_named_list("a"), error = TRUE)
-  expect_snapshot(assert_named_list(list("a", "b")), error = TRUE)
+  expect_snapshot_igraph_error(set_vertex_attr(g, "test", value = c(1, 2)))
+  expect_snapshot_igraph_error(set_edge_attr(g, "test", value = c(1, 2)))
+  expect_snapshot_igraph_error(delete_graph_attr(g, "a"))
+  expect_snapshot_igraph_error(delete_vertex_attr(g, "a"))
+  expect_snapshot_igraph_error(delete_edge_attr(g, "a"))
+  expect_snapshot_igraph_error(assert_named_list("a"))
+  expect_snapshot_igraph_error(assert_named_list(list("a", "b")))
 })
 
 test_that("empty returns work", {
@@ -465,7 +465,7 @@ test_that("assign data.frame attributes works", {
 
 test_that("good error message when not using character", {
   ring <- graph_from_literal(A - B - C - D - E - F - G - A)
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     set_graph_attr(ring, 1, 1)
   })
 })
@@ -476,7 +476,7 @@ test_that("set_vertex_attrs() works", {
   expect_equal(V(g)$color, rep("blue", vcount(g)))
   expect_equal(V(g)$size, rep(10, vcount(g)))
   expect_equal(V(g)$name, LETTERS[1:10])
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     set_vertex_attrs(g)
   })
 
diff --git a/tests/testthat/test-centrality.R b/tests/testthat/test-centrality.R
index 65e0a407c0c..71bd753a7e6 100644
--- a/tests/testthat/test-centrality.R
+++ b/tests/testthat/test-centrality.R
@@ -848,7 +848,7 @@ test_that("arpack() errors well", {
   expect_snapshot_igraph_error({
     arpack(f, options = list(nev = 2, ncv = 4), sym = TRUE)
   })
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     arpack(
       f,
       options = list(unknown_thing1 = 2, unknown_thing2 = 4),
diff --git a/tests/testthat/test-conversion.R b/tests/testthat/test-conversion.R
index 5fddb5f12fb..367e4d7d068 100644
--- a/tests/testthat/test-conversion.R
+++ b/tests/testthat/test-conversion.R
@@ -142,10 +142,10 @@ test_that("as_adjacency_matrix() works -- sparse + not both", {
 
 test_that("as_adjacency_matrix() errors well -- sparse", {
   g <- make_graph(c(1, 2, 2, 1, 2, 2, 3, 3, 3, 3, 3, 4, 4, 2, 4, 2, 4, 2), directed = TRUE)
-  expect_snapshot(as_adjacency_matrix(g, attr = "bla"), error = TRUE)
+  expect_snapshot_igraph_error(as_adjacency_matrix(g, attr = "bla"))
 
   E(g)$bla <- letters[1:ecount(g)]
-  expect_snapshot(as_adjacency_matrix(g, attr = "bla"), error = TRUE)
+  expect_snapshot_igraph_error(as_adjacency_matrix(g, attr = "bla"))
 })
 
 test_that("as_adjacency_matrix() works -- sparse undirected", {
@@ -679,7 +679,7 @@ test_that("edge names work", {
 
 test_that("graph_from_edgelist errors for NAs", {
   A <- matrix(c(1, 2, NA, 1), 2, 2)
-  expect_snapshot(graph_from_edgelist(A), error = TRUE)
+  expect_snapshot_igraph_error(graph_from_edgelist(A))
 })
 
 test_that("graph_from_data_frame works with factors", {
diff --git a/tests/testthat/test-error-formatting.R b/tests/testthat/test-error-formatting.R
index 5e19acb2a66..a29e5d59c7e 100644
--- a/tests/testthat/test-error-formatting.R
+++ b/tests/testthat/test-error-formatting.R
@@ -1,4 +1,8 @@
 test_that("error messages include source file and line information", {
+  # Note: We use expect_snapshot(error = TRUE) here instead of
+  # expect_snapshot_igraph_error() because we need to test the actual
+  # line numbers in the error message, which expect_snapshot_igraph_error()
+  # would transform to "xx".
   expect_snapshot(
     error = TRUE,
     {
diff --git a/tests/testthat/test-fit.R b/tests/testthat/test-fit.R
index 0b6019461e0..67cb5288880 100644
--- a/tests/testthat/test-fit.R
+++ b/tests/testthat/test-fit.R
@@ -28,7 +28,7 @@ test_that("fit_power_law() works", {
 })
 
 test_that("fit_power_law() errors well", {
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     fit_power_law(1, implementation = "R.mle")
   })
 })
diff --git a/tests/testthat/test-flow.R b/tests/testthat/test-flow.R
index 3083a8bbf72..c620a0900da 100644
--- a/tests/testthat/test-flow.R
+++ b/tests/testthat/test-flow.R
@@ -98,8 +98,8 @@ test_that("st_cuts() works", {
 test_that("st_cuts errors work", {
   g_path <- graph_from_literal(a -+ b -+ c -+ d -+ e)
 
-  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_igraph_error(st_cuts(g_path, source = "a", target = NULL))
+  expect_snapshot_igraph_error(st_cuts(g_path, source = NULL, target = "a"))
   expect_snapshot(
     st_min_cuts(g_path, source = "a", target = NULL),
     error = TRUE
@@ -142,7 +142,7 @@ test_that("vertex_connectivity() works", {
 
 test_that("vertex_connectivity error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_snapshot(vertex_connectivity(g_path, source = 1), error = TRUE)
+  expect_snapshot_igraph_error(vertex_connectivity(g_path, source = 1))
 })
 
 test_that("edge_connectivity works", {
@@ -179,7 +179,7 @@ test_that("edge_connectivity works -- names", {
 
 test_that("edge_connectivity error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_snapshot(edge_connectivity(g_path, source = 1), error = TRUE)
+  expect_snapshot_igraph_error(edge_connectivity(g_path, source = 1))
 })
 
 test_that("edge_disjoint_paths works", {
@@ -212,7 +212,7 @@ test_that("vertex_disjoint_paths works", {
 
 test_that("vertex_disjoint_paths error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_snapshot(vertex_disjoint_paths(g_path, source = 1), error = TRUE)
+  expect_snapshot_igraph_error(vertex_disjoint_paths(g_path, source = 1))
 })
 
 test_that("adhesion works", {
@@ -225,7 +225,7 @@ test_that("adhesion works", {
 
 test_that("vertex_disjoint_paths error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_snapshot(vertex_disjoint_paths(g_path, source = 1), error = TRUE)
+  expect_snapshot_igraph_error(vertex_disjoint_paths(g_path, source = 1))
 })
 
 
@@ -252,8 +252,8 @@ test_that("dominator_tree errors work", {
     matrix(c(1, 2, 2, 3, 3, 4, 2, 5, 5, 6), byrow = TRUE, ncol = 2),
     directed = TRUE
   )
-  expect_snapshot(dominator_tree(g_tree), error = TRUE)
-  expect_snapshot(dominator_tree(g_tree, root = NULL), error = TRUE)
+  expect_snapshot_igraph_error(dominator_tree(g_tree))
+  expect_snapshot_igraph_error(dominator_tree(g_tree, root = NULL))
 })
 
 test_that("dominator_tree works -- legacy", {
diff --git a/tests/testthat/test-foreign.R b/tests/testthat/test-foreign.R
index 75f2c7a53f3..54b2b90c3b3 100644
--- a/tests/testthat/test-foreign.R
+++ b/tests/testthat/test-foreign.R
@@ -49,17 +49,17 @@ test_that("reading graph, unused argument", {
   lgl_path <- withr::local_tempfile(pattern = "testfile", fileext = ".lgl")
   g <- make_graph(c(1, 2, 2, 3))
   write_graph(g, lgl_path, "lgl")
-  expect_snapshot(error = TRUE, read_graph(lgl_path, "lgl", useless = 1))
+  expect_snapshot_igraph_error(read_graph(lgl_path, "lgl", useless = 1))
 })
 
 test_that("reading graph in unsupported format", {
-  expect_snapshot(error = TRUE, read_graph("bla", format = "blop"))
+  expect_snapshot_igraph_error(read_graph("bla", format = "blop"))
 })
 
 test_that("writing graph in unsupported format", {
   g <- make_graph(c(1, 2, 2, 3))
   file <- withr::local_tempfile()
-  expect_snapshot(error = TRUE, write_graph(g, file, format = "blop"))
+  expect_snapshot_igraph_error(write_graph(g, file, format = "blop"))
 })
 
 test_that("graph_from_graphdb works", {
@@ -72,7 +72,7 @@ test_that("graph_from_graphdb works", {
   skip_if(Sys.getenv("R_SANITIZER") == "true")
 
   expect_snapshot(g <- graph_from_graphdb(nodes = 1000))
-  expect_snapshot(g <- graph_from_graphdb(), error = TRUE)
+  expect_snapshot_igraph_error(g <- graph_from_graphdb())
   expect_snapshot(
     g <- graph_from_graphdb(nodes = 10, prefix = "not_existing"),
     error = TRUE
diff --git a/tests/testthat/test-hrg.R b/tests/testthat/test-hrg.R
index 381d9669ab1..cbb22bc7c27 100644
--- a/tests/testthat/test-hrg.R
+++ b/tests/testthat/test-hrg.R
@@ -18,14 +18,14 @@ test_that("as.hclust.igraphHRG() works", {
 })
 
 test_that("sample_hrg() checks its argument", {
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     sample_hrg(make_ring(10))
   })
 })
 
 
 test_that("hrg_tree() checks its argument", {
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     hrg_tree(make_ring(10))
   })
 })
diff --git a/tests/testthat/test-incidence.R b/tests/testthat/test-incidence.R
index 3f4b1ba7c43..68b5fb34d03 100644
--- a/tests/testthat/test-incidence.R
+++ b/tests/testthat/test-incidence.R
@@ -216,18 +216,18 @@ test_that("graph_from_biadjacency_matrix() errors well", {
   colnames(inc) <- letters[1:5]
   rownames(inc) <- LETTERS[1:3]
 
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     (g <- graph_from_biadjacency_matrix(inc, weight = FALSE))
   })
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     (g <- graph_from_biadjacency_matrix(inc, weight = 42))
   })
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     (g <- graph_from_biadjacency_matrix(inc, multiple = TRUE, weighted = TRUE))
   })
 })
 
 test_that("graph_from_biadjacency_matrix errors for NAs", {
   A <- matrix(c(1, 1, NA, 1), 2, 2)
-  expect_snapshot(graph_from_biadjacency_matrix(A), error = TRUE)
+  expect_snapshot_igraph_error(graph_from_biadjacency_matrix(A))
 })
diff --git a/tests/testthat/test-interface.R b/tests/testthat/test-interface.R
index 0d331bda8fc..ff287fbb0a3 100644
--- a/tests/testthat/test-interface.R
+++ b/tests/testthat/test-interface.R
@@ -181,7 +181,7 @@ test_that("ends works", {
 test_that("get.edge.ids() deprecation", {
   g <- make_empty_graph(10)
   expect_snapshot(get.edge.ids(g, 1:2))
-  expect_snapshot(get.edge.ids(g, 1:2, multi = TRUE), error = TRUE)
+  expect_snapshot_igraph_error(get.edge.ids(g, 1:2, multi = TRUE))
 })
 
 test_that("get_edge_id() works with data frame", {
@@ -202,7 +202,7 @@ test_that("get_edge_id() works with matrices", {
 test_that("get_edge_id() errors correctly for wrong vp", {
   g <- make_full_graph(3, directed = FALSE)
   el_g <- make_empty_graph()
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     get_edge_ids(g, el_g)
   })
   expect_error(get_edge_ids(g, NULL))
@@ -210,7 +210,7 @@ test_that("get_edge_id() errors correctly for wrong vp", {
 
   V(g)$name <- letters[1:3]
   df <- data.frame(from = c("a", "b"), to = c(1, 2))
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     get_edge_ids(g, df)
   })
 })
diff --git a/tests/testthat/test-iterators.R b/tests/testthat/test-iterators.R
index 50790e1623a..a4acfe64974 100644
--- a/tests/testthat/test-iterators.R
+++ b/tests/testthat/test-iterators.R
@@ -444,6 +444,6 @@ test_that("edge indexes are stored as raw numbers", {
 test_that("logical indices are not recycled", {
   # https://github.com/igraph/rigraph/issues/848
   g <- make_ring(5)
-  expect_snapshot(V(g)[c(TRUE, FALSE)], error = TRUE)
-  expect_snapshot(E(g)[c(TRUE, FALSE)], error = TRUE)
+  expect_snapshot_igraph_error(V(g)[c(TRUE, FALSE)])
+  expect_snapshot_igraph_error(E(g)[c(TRUE, FALSE)])
 })
diff --git a/tests/testthat/test-layout.R b/tests/testthat/test-layout.R
index e1c6b22727b..725c966c0fc 100644
--- a/tests/testthat/test-layout.R
+++ b/tests/testthat/test-layout.R
@@ -17,7 +17,7 @@ test_that("layout_with_fr() works", {
 test_that("layout_with_fr() deprecated argument", {
   rlang::local_options(lifecycle_verbosity = "warning")
   g <- make_ring(10)
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     l <- layout_with_fr(
       g,
       niter = 50,
@@ -212,7 +212,7 @@ test_that("Kamada-Kawai layout generator works", {
 
 test_that("layout_with_kk() deprecated arguments", {
   g <- make_ring(10)
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     l <- layout_with_kk(
       g,
       maxiter = 50,
@@ -334,7 +334,7 @@ test_that("add_layout_ works", {
 
 test_that("layout_randomly() errors well", {
   g <- make_empty_graph(1)
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     layout_randomly(g, dim = 4)
   })
 })
diff --git a/tests/testthat/test-make.R b/tests/testthat/test-make.R
index c925cb88529..e5708c593ba 100644
--- a/tests/testthat/test-make.R
+++ b/tests/testthat/test-make.R
@@ -292,9 +292,9 @@ test_that("compatibility when arguments are not named", {
 })
 
 test_that("make_empty_graph gives an error for invalid arguments", {
-  expect_snapshot(make_empty_graph(NULL), error = TRUE)
-  expect_snapshot(make_empty_graph("spam"), error = TRUE)
-  expect_snapshot(make_empty_graph(10, "spam"), error = TRUE)
+  expect_snapshot_igraph_error(make_empty_graph(NULL))
+  expect_snapshot_igraph_error(make_empty_graph("spam"))
+  expect_snapshot_igraph_error(make_empty_graph(10, "spam"))
 })
 
 test_that("make_graph_atlas works", {
diff --git a/tests/testthat/test-other.R b/tests/testthat/test-other.R
index 6ccd5cf2c45..02bf0248d5b 100644
--- a/tests/testthat/test-other.R
+++ b/tests/testthat/test-other.R
@@ -159,7 +159,7 @@ karate <- structure(
 )
 
 test_that("VS/ES require explicit conversion", {
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     V(karate)
   })
 })
diff --git a/tests/testthat/test-plot.R b/tests/testthat/test-plot.R
index 1467da59594..bbc29010ab8 100644
--- a/tests/testthat/test-plot.R
+++ b/tests/testthat/test-plot.R
@@ -142,7 +142,7 @@ test_that("Edges stop at outside of rectangle node", {
 test_that("layout as graph attribute error works", {
   g <- make_full_graph(10)
   g$layout <- layout_in_circle(g)[1:5, ]
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     plot(g)
   })
 })
diff --git a/tests/testthat/test-structural-properties.R b/tests/testthat/test-structural-properties.R
index 422e615f969..ac8f7936a8d 100644
--- a/tests/testthat/test-structural-properties.R
+++ b/tests/testthat/test-structural-properties.R
@@ -20,7 +20,7 @@ test_that("dfs() does not pad order", {
 test_that("dfs() deprecated arguments", {
   g <- make_star(3)
 
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     d <- dfs(
       g,
       root = 2,
@@ -235,7 +235,7 @@ test_that("bfs() works", {
 test_that("bfs() deprecated arguments", {
   g <- graph_from_literal(a -+ b -+ c, z -+ a, d)
 
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     b <- bfs(
       g,
       root = 2,
diff --git a/tests/testthat/test-versions.R b/tests/testthat/test-versions.R
index 2429e227c24..0af0633de57 100644
--- a/tests/testthat/test-versions.R
+++ b/tests/testthat/test-versions.R
@@ -6,7 +6,7 @@ test_that("we create graphs of the current version", {
 })
 
 test_that("we can't upgrade from 0.1.1 to 1.5.0, on the fly", {
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     oldsample_0_1_1()
   })
 })
@@ -16,13 +16,13 @@ test_that("we can't upgrade from 0.1.1 to 1.5.0, explicitly", {
 
   expect_equal(graph_version(g), ver_0_1_1)
 
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     upgrade_graph(g)
   })
 })
 
 test_that("we can't upgrade from 0.2 to 1.5.0, on the fly", {
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     oldsample_0_2()
   })
 })
@@ -37,7 +37,7 @@ test_that("we can upgrade from 0.2 to 1.5.0, explicitly", {
 })
 
 test_that("we can't upgrade from 0.5 to 1.5.0, on the fly", {
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     oldsample_0_5()
   })
 })
@@ -52,7 +52,7 @@ test_that("we can upgrade from 0.5 to 1.5.0, explicitly", {
 })
 
 test_that("we can't upgrade from 0.6 to 1.5.0, on the fly", {
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     oldsample_0_6()
   })
 })
@@ -95,16 +95,16 @@ test_that("reading of old igraph formats", {
   local_igraph_options(print.id = FALSE)
 
   s <- oldsamples()
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     s[["0.1.1"]]
   })
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     s[["0.2"]]
   })
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     s[["0.5"]]
   })
-  expect_snapshot(error = TRUE, {
+  expect_snapshot_igraph_error({
     s[["0.6"]]
   })
   expect_snapshot({

From b56ed3bac0a0de6a59415105866b0bbb4cec181a Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 24 Jan 2026 10:01:15 +0000
Subject: [PATCH 3/5] fix: add test_error_with_source.o to build and update
 snapshot

Co-authored-by: krlmlr <1741643+krlmlr@users.noreply.github.com>
---
 src/sources-glue-c.mk                              |  2 +-
 src/test_error_with_source.dd                      |  4 ++++
 .../testthat/_problems/test-error-formatting-11.R  | 14 ++++++++++++++
 tests/testthat/_snaps/error-formatting.md          |  2 +-
 4 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 src/test_error_with_source.dd
 create mode 100644 tests/testthat/_problems/test-error-formatting-11.R

diff --git a/src/sources-glue-c.mk b/src/sources-glue-c.mk
index a0ca36b78c0..3508954fced 100644
--- a/src/sources-glue-c.mk
+++ b/src/sources-glue-c.mk
@@ -1 +1 @@
-GLUE_C_SOURCES=rcallback.o rinterface.o rinterface_extra.o rrandom.o uuid.o
+GLUE_C_SOURCES=rcallback.o rinterface.o rinterface_extra.o rrandom.o test_error_with_source.o uuid.o
diff --git a/src/test_error_with_source.dd b/src/test_error_with_source.dd
new file mode 100644
index 00000000000..3eea9c3527c
--- /dev/null
+++ b/src/test_error_with_source.dd
@@ -0,0 +1,4 @@
+# Generated by deps.mk, do not edit by hand and do not add dependencies to system headers
+test_error_with_source.o: \
+  rinterface.h \
+  test_error_with_source.c \
diff --git a/tests/testthat/_problems/test-error-formatting-11.R b/tests/testthat/_problems/test-error-formatting-11.R
new file mode 100644
index 00000000000..dcf2fa7f4eb
--- /dev/null
+++ b/tests/testthat/_problems/test-error-formatting-11.R
@@ -0,0 +1,14 @@
+# Extracted from test-error-formatting.R:11
+
+# setup ------------------------------------------------------------------------
+library(testthat)
+test_env <- simulate_test_env(package = "igraph", path = "..")
+attach(test_env, warn.conflicts = FALSE)
+
+# test -------------------------------------------------------------------------
+expect_snapshot(
+    error = TRUE,
+    {
+      test_error_with_source()
+    }
+  )
diff --git a/tests/testthat/_snaps/error-formatting.md b/tests/testthat/_snaps/error-formatting.md
index fca0e7ab3a1..66512692f0e 100644
--- a/tests/testthat/_snaps/error-formatting.md
+++ b/tests/testthat/_snaps/error-formatting.md
@@ -5,5 +5,5 @@
     Condition
       Error in `test_error_with_source()`:
       ! Test error message for verifying source location formatting. Invalid value
-      Source: rinterface_extra.c:7766
+      Source: test_error_with_source.c:31
 

From e42ebce6a08a6a31685ba3d7b372a9d1c5f07a7d Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 24 Jan 2026 10:01:23 +0000
Subject: [PATCH 4/5] chore: remove test problems file

Co-authored-by: krlmlr <1741643+krlmlr@users.noreply.github.com>
---
 .../testthat/_problems/test-error-formatting-11.R  | 14 --------------
 1 file changed, 14 deletions(-)
 delete mode 100644 tests/testthat/_problems/test-error-formatting-11.R

diff --git a/tests/testthat/_problems/test-error-formatting-11.R b/tests/testthat/_problems/test-error-formatting-11.R
deleted file mode 100644
index dcf2fa7f4eb..00000000000
--- a/tests/testthat/_problems/test-error-formatting-11.R
+++ /dev/null
@@ -1,14 +0,0 @@
-# Extracted from test-error-formatting.R:11
-
-# setup ------------------------------------------------------------------------
-library(testthat)
-test_env <- simulate_test_env(package = "igraph", path = "..")
-attach(test_env, warn.conflicts = FALSE)
-
-# test -------------------------------------------------------------------------
-expect_snapshot(
-    error = TRUE,
-    {
-      test_error_with_source()
-    }
-  )

From 4a4a59993816c218fbbeb4c0a2344c7b07216301 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 24 Jan 2026 10:18:19 +0000
Subject: [PATCH 5/5] fix: transform remaining multi-line expect_snapshot with
 error = TRUE

Co-authored-by: krlmlr <1741643+krlmlr@users.noreply.github.com>
---
 tests/testthat/test-conversion.R            | 10 ++++------
 tests/testthat/test-flow.R                  | 20 ++++++++------------
 tests/testthat/test-foreign.R               | 10 ++++------
 tests/testthat/test-make.R                  |  5 ++---
 tests/testthat/test-minimum.spanning.tree.R |  5 ++---
 tests/testthat/test-other.R                 |  5 ++---
 tests/testthat/test-utils-assert-args.R     |  5 ++---
 7 files changed, 24 insertions(+), 36 deletions(-)

diff --git a/tests/testthat/test-conversion.R b/tests/testthat/test-conversion.R
index 367e4d7d068..65a2858fc67 100644
--- a/tests/testthat/test-conversion.R
+++ b/tests/testthat/test-conversion.R
@@ -197,15 +197,13 @@ test_that("as_adjacency_matrix() works -- dense", {
 
 test_that("as_adjacency_matrix() errors well -- dense", {
   g <- make_graph(c(1, 2, 2, 1, 2, 2, 3, 3, 3, 3, 3, 4, 4, 2, 4, 2, 4, 2), directed = TRUE)
-  expect_snapshot(
-    as_adjacency_matrix(g, attr = "bla", sparse = FALSE),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    as_adjacency_matrix(g, attr = "bla", sparse = FALSE)
   )
 
   E(g)$bla <- letters[1:ecount(g)]
-  expect_snapshot(
-    as_adjacency_matrix(g, attr = "bla", sparse = FALSE),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    as_adjacency_matrix(g, attr = "bla", sparse = FALSE)
   )
 })
 
diff --git a/tests/testthat/test-flow.R b/tests/testthat/test-flow.R
index c620a0900da..d9b9eec71d5 100644
--- a/tests/testthat/test-flow.R
+++ b/tests/testthat/test-flow.R
@@ -100,13 +100,11 @@ test_that("st_cuts errors work", {
 
   expect_snapshot_igraph_error(st_cuts(g_path, source = "a", target = NULL))
   expect_snapshot_igraph_error(st_cuts(g_path, source = NULL, target = "a"))
-  expect_snapshot(
-    st_min_cuts(g_path, source = "a", target = NULL),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    st_min_cuts(g_path, source = "a", target = NULL)
   )
-  expect_snapshot(
-    st_min_cuts(g_path, source = NULL, target = "a"),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    st_min_cuts(g_path, source = NULL, target = "a")
   )
 })
 
@@ -192,13 +190,11 @@ test_that("edge_disjoint_paths works", {
 
 test_that("edge_disjoint_paths error works", {
   g_path <- make_ring(5, circular = FALSE)
-  expect_snapshot(
-    edge_disjoint_paths(g_path, source = 1, target = NULL),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    edge_disjoint_paths(g_path, source = 1, target = NULL)
   )
-  expect_snapshot(
-    edge_disjoint_paths(g_path, source = NULL, target = 1),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    edge_disjoint_paths(g_path, source = NULL, target = 1)
   )
 })
 
diff --git a/tests/testthat/test-foreign.R b/tests/testthat/test-foreign.R
index 54b2b90c3b3..3a26f55e8b7 100644
--- a/tests/testthat/test-foreign.R
+++ b/tests/testthat/test-foreign.R
@@ -73,12 +73,10 @@ test_that("graph_from_graphdb works", {
 
   expect_snapshot(g <- graph_from_graphdb(nodes = 1000))
   expect_snapshot_igraph_error(g <- graph_from_graphdb())
-  expect_snapshot(
-    g <- graph_from_graphdb(nodes = 10, prefix = "not_existing"),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    g <- graph_from_graphdb(nodes = 10, prefix = "not_existing")
   )
-  expect_snapshot(
-    g <- graph_from_graphdb(nodes = 10, type = "not_existing"),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    g <- graph_from_graphdb(nodes = 10, type = "not_existing")
   )
 })
diff --git a/tests/testthat/test-make.R b/tests/testthat/test-make.R
index e5708c593ba..ca8b9c658c8 100644
--- a/tests/testthat/test-make.R
+++ b/tests/testthat/test-make.R
@@ -42,7 +42,7 @@ test_that("sample_, graph_ also work", {
 
 test_that("error messages are proper", {
   rlang::local_options(lifecycle_verbosity = "quiet")
-  expect_snapshot(
+  expect_snapshot_igraph_error(
     {
       make_()
       make_(1:10)
@@ -54,8 +54,7 @@ test_that("error messages are proper", {
       sample_()
       sample_(1:10)
       sample_(directed_graph(), directed_graph())
-    },
-    error = TRUE
+    }
   )
 })
 
diff --git a/tests/testthat/test-minimum.spanning.tree.R b/tests/testthat/test-minimum.spanning.tree.R
index c6422d7a385..3fddd46813b 100644
--- a/tests/testthat/test-minimum.spanning.tree.R
+++ b/tests/testthat/test-minimum.spanning.tree.R
@@ -34,8 +34,7 @@ test_that("mst works", {
 
 test_that("mst error works", {
   g <- sample_gnp(10, 0.4)
-  expect_snapshot(
-    mst(g, algorithm = "undefined"),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    mst(g, algorithm = "undefined")
   )
 })
diff --git a/tests/testthat/test-other.R b/tests/testthat/test-other.R
index 02bf0248d5b..063ab5a13e9 100644
--- a/tests/testthat/test-other.R
+++ b/tests/testthat/test-other.R
@@ -29,9 +29,8 @@ test_that("can create graphs when igraph is not attached", {
 
 test_that("running_mean works", {
   expect_equal(running_mean(1:10, 2), 2:10 - 0.5)
-  expect_snapshot(
-    running_mean(1:3, 4),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    running_mean(1:3, 4)
   )
 })
 
diff --git a/tests/testthat/test-utils-assert-args.R b/tests/testthat/test-utils-assert-args.R
index a2984d3a94b..d2b2654a3b2 100644
--- a/tests/testthat/test-utils-assert-args.R
+++ b/tests/testthat/test-utils-assert-args.R
@@ -7,8 +7,7 @@ test_that("ensure_igraph() works", {
 })
 
 test_that("igraph_match_arg() works", {
-  expect_snapshot(
-    cluster_leiden(make_graph("Zachary"), objective_function = "something"),
-    error = TRUE
+  expect_snapshot_igraph_error(
+    cluster_leiden(make_graph("Zachary"), objective_function = "something")
   )
 })