test: add tests for as_adjacency_matrix

Author: maelle

tests/testthat/_snaps/conversion.md

@@ -0,0 +1,10 @@
+# as_adjacency_matrix() works
+
+    Code
+      as_adjacency_matrix(example_graph, sparse = TRUE)
+    Output
+      2 x 2 sparse Matrix of class "dgCMatrix"
+              
+      [1,] 1 1
+      [2,] 1 .
+

tests/testthat/test-conversion.R

@@ -0,0 +1,21 @@
+test_that("as_adjacency_matrix() works", {
+  # https://github.com/igraph/rigraph/issues/1429
+  a_matrix <- (matrix(sample(rep(c(0,1),8)), nrow = 4, ncol = 4))
+  ig <- graph_from_adjacency_matrix(a_matrix, mode = "directed")
+  b_matrix <- as_adjacency_matrix(ig, sparse = FALSE)
+  expect_identical(diag(a_matrix), diag(b_matrix))
+
+  expect_identical(
+    as_adjacency_matrix(make_graph(c(1,1)), sparse = FALSE),
+    matrix(1)
+  )
+
+  example_graph <- make_graph(c(1,1, 1,2), directed = FALSE)
+  expect_identical(
+    as_adjacency_matrix(example_graph, sparse = FALSE),
+    matrix(c(1, 1, 1, 0), nrow = 2, ncol = 2)
+  )
+  expect_snapshot(
+    as_adjacency_matrix(example_graph, sparse = TRUE)
+  )
+})