Write tests for as_igraph and fix small bug

Author: frederikfabriciusbjerre

R/as_igraph.R

@@ -38,7 +38,7 @@ as_igraph <- function(x, ...) {
   }
 
   # edge validity for Unknown
-  if (x@graph_class == "Unknown") {
+  if (x@graph_class == "UNKNOWN") {
     if (any(!(et %in% c("-->", "<->", "---")))) {
       stop("Conversion to igraph is only supported for 'Unknown' caugi graphs ",
         " with '-->', '<->', or '---' edges.",

tests/testthat/test-as_igraph.R

@@ -0,0 +1,96 @@
+test_that("cg --> as_igraph --> as_caugi --> as_igraph works for directed", {
+  cg <- caugi_graph(
+    A %-->% B + C,
+    B %-->% D,
+    C %-->% D,
+    E %-->% F,
+    class = "DAG"
+  )
+
+  ig <- as_igraph(cg)
+  cg2 <- as_caugi(ig, class = "DAG")
+
+  ig2 <- as_igraph(cg2)
+  expect_equal(igraph::V(ig)$name, igraph::V(ig2)$name)
+  expect_equal(igraph::as_data_frame(ig), igraph::as_data_frame(ig2))
+  expect_equal(nodes(cg), nodes(cg2))
+  expect_equal(edges(cg), edges(cg2))
+})
+
+test_that("errors on non-caugi input", {
+  expect_error(as_igraph("not-a-caugi"))
+})
+
+
+test_that("Unknown graph with undirected edges become undirected igraph", {
+  cg <- caugi_graph(A %---% B + C,
+    C %---% D,
+    class = "Unknown"
+  )
+  ig <- as_igraph(cg)
+  expect_false(igraph::is_directed(ig))
+})
+
+test_that("Unknown with PAG edges fails", {
+  cg <- caugi_graph(A %o-o% B %o->% C, class = "Unknown")
+  expect_error(as_igraph(cg))
+})
+
+test_that("empty graph handled with given vertices", {
+  # Only nodes, no edges
+  cg <- caugi_graph(A, B, C, class = "DAG")
+  ig <- as_igraph(cg)
+  expect_true(all(sort(igraph::V(ig)$name) == sort(nodes(cg)$name)))
+  expect_equal(nrow(igraph::as_data_frame(ig)), 0L)
+  # Directedness defaults to FALSE when no edge types present
+  expect_false(igraph::is_directed(ig))
+})
+
+test_that("all undirected edge types yield undirected igraph", {
+  cg <- caugi_graph(A %---% B %<->% C, class = "Unknown")
+  ig <- as_igraph(cg)
+  expect_false(igraph::is_directed(ig))
+  ed <- igraph::as_data_frame(ig)
+  # undirected collapsed
+  expect_true(any(ed$from == "A" & ed$to == "B") || any(ed$from == "B" & ed$to == "A"))
+  expect_true(any(ed$from == "B" & ed$to == "C") || any(ed$from == "C" & ed$to == "B"))
+  # no duplicates
+  expect_equal(nrow(ed), 2L)
+})
+
+test_that("all directed edges yield directed igraph", {
+  cg <- caugi_graph(
+    A %-->% B,
+    B %-->% C,
+    D %-->% C,
+    class = "DAG"
+  )
+  ig <- as_igraph(cg)
+  expect_true(igraph::is_directed(ig))
+  ed <- igraph::as_data_frame(ig)
+  expect_true(all(ed$from %in% c("A", "B", "D")))
+  expect_true(all(ed$to %in% c("B", "C")))
+  expect_equal(nrow(ed), 3L)
+})
+
+test_that("mixed edges: directed kept, undirected duplicated as bidirected", {
+  cg <- caugi_graph(
+    A %-->% B,
+    B %---% C,
+    C %---% D,
+    class = "PDAG"
+  )
+  ig <- as_igraph(cg)
+  expect_true(igraph::is_directed(ig))
+  ed <- igraph::as_data_frame(ig)
+  # A->B remains single
+  expect_true(any(ed$from == "A" & ed$to == "B"))
+  # B---C becomes B->C and C->B
+  expect_true(any(ed$from == "B" & ed$to == "C"))
+  expect_true(any(ed$from == "C" & ed$to == "B"))
+  # C<->D becomes C->D and D->C
+  expect_true(any(ed$from == "C" & ed$to == "D"))
+  expect_true(any(ed$from == "D" & ed$to == "C"))
+  # total edges: 1 directed + 2*undirected (2 undirected edges) = 5
+  expect_equal(nrow(ed), 5L)
+})