test: Pin the results that the igraph C core 1.0 changes

tests/testthat/test-adjacency.R

@@ -1002,3 +1002,10 @@ test_that("from_adjacency() covers tail args by name and recovers positional cal
     make_(from_adjacency(M, mode = "undirected"))
   )
 })
+
+test_that("graph_from_adjacency_matrix() creates edges row by row", {
+  # Pins the edge order of the C core for directed input.
+  m <- matrix(c(0, 1, 1, 1, 0, 1, 0, 0, 0), 3)
+  g <- graph_from_adjacency_matrix(m)
+  expect_equal(as_edgelist(g), rbind(c(1, 2), c(2, 1), c(3, 1), c(3, 2)))
+})

tests/testthat/test-centrality.R

@@ -594,9 +594,20 @@ test_that("eigen_centrality() works", {
     expect_ev(M, v, lambda, eps)
   }
 
+  # Most of these graphs are disconnected, and warn that some centralities
+  # are nearly zero; no other warning is expected.
   for (i in 1:1000) {
     G <- sample_gnm(10, sample(1:20, 1))
-    ev <- eigen_centrality(G)
+    ev <- withCallingHandlers(
+      eigen_centrality(G),
+      warning = function(w) {
+        expect_match(
+          conditionMessage(w),
+          "eigenvector centralities are nearly zero"
+        )
+        invokeRestart("muffleWarning")
+      }
+    )
     expect_good(
       as_adjacency_matrix(G, sparse = FALSE),
       ev$vector,
@@ -1258,3 +1269,28 @@ test_that("alpha_centrality() covers migrated tail args and positional recovery"
   )
   expect_identical(res_legacy, alpha_centrality(dag, V(dag), alpha = 0.75))
 })
+
+# ---- C core behaviour pins ----------------------------------------------
+# These pin the behaviour of the vendored C core,
+# so that the vendor commit that changes it also flips the expectation.
+
+test_that("hits_scores() on an edgeless graph gives NaN silently", {
+  g <- make_empty_graph(3)
+  expect_silent(res <- hits_scores(g))
+  expect_identical(res$value, NaN)
+})
+
+test_that("hits_scores() on an undirected graph does not warn", {
+  expect_silent(res <- hits_scores(make_ring(3)))
+  expect_equal(res$value, 4)
+})
+
+test_that("eigen_centrality() on a disconnected graph does not warn", {
+  g <- make_star(3, mode = "undirected") + make_ring(3)
+  expect_silent(res <- eigen_centrality(g))
+  expect_equal(res$vector, c(0, 0, 0, 1, 1, 1))
+
+  g <- make_ring(3) + make_ring(4)
+  expect_silent(res <- eigen_centrality(g))
+  expect_equal(res$vector, rep(1, 7), tolerance = 1e-5)
+})

tests/testthat/test-community.R

@@ -1042,3 +1042,10 @@ test_that("modularity_matrix() covers migrated tail args and positional recovery
     modularity_matrix(karate, rep(1, vcount(karate)), rep(1, ecount(karate)))
   })
 })
+
+test_that("cluster_infomap() code length on the karate graph", {
+  # Pins the vendored Infomap implementation.
+  karate <- make_graph("Zachary")
+  res <- cluster_infomap(karate, nb.trials = 1)
+  expect_equal(code_len(res), 4.606059, tolerance = 1e-6)
+})

tests/testthat/test-games.R

@@ -1770,3 +1770,13 @@ test_that("sample_correlated_gnp() recovers positional p", {
     sample_correlated_gnp(base_graph, 0.8, p = 0.3)
   )
 })
+
+test_that("sample_islands() random stream for a fixed seed", {
+  # Pins the random numbers the C core draws for this generator.
+  igraph_local_seed(42)
+  g <- sample_islands(2, 3, 0.5, 1)
+  expect_equal(
+    as_edgelist(g),
+    rbind(c(1, 3), c(2, 3), c(3, 6), c(4, 5), c(4, 6))
+  )
+})

tests/testthat/test-incidence.R

@@ -251,3 +251,10 @@ test_that("graph_from_biadjacency_matrix() covers add.names by name and recovers
   )
   expect_true(is_directed(res))
 })
+
+test_that("graph_from_biadjacency_matrix() creates edges row by row", {
+  # Pins the edge order of the C core for dense unweighted input.
+  m <- matrix(c(1, 1, 1, 0), 2)
+  g <- graph_from_biadjacency_matrix(m)
+  expect_equal(as_edgelist(g), rbind(c(1, 3), c(1, 4), c(2, 3)))
+})

tests/testthat/test-layout.R

@@ -945,3 +945,25 @@ test_that("norm_coords() recovers positional calls", {
   # xmin = 0 rescales the first column into [0, 1].
   expect_equal(range(res[, 1]), c(0, 1))
 })
+
+test_that("layout_with_gem() random stream for a fixed seed", {
+  # Pins the random numbers the C core draws for this layout.
+  igraph_local_seed(42)
+  l <- layout_with_gem(make_ring(3))
+  expect_equal(
+    l,
+    cbind(c(130.218, -34.753, 88.118), c(238.780, 196.748, 71.715)),
+    tolerance = 1e-4
+  )
+})
+
+test_that("layout_with_dh() random stream for a fixed seed", {
+  # Pins the random numbers the C core draws for this layout.
+  igraph_local_seed(42)
+  l <- layout_with_dh(make_ring(3))
+  expect_equal(
+    l,
+    cbind(c(0.444, -1.310, -0.350), c(-7.937, -7.812, -6.384)),
+    tolerance = 1e-3
+  )
+})