1 files changed, 11 insertions, 0 deletions
diff --git a/src/test/scala/firrtlTests/graph/DiGraphTests.scala b/src/test/scala/firrtlTests/graph/DiGraphTests.scala
index 84122f83..b9f51699 100644
--- a/src/test/scala/firrtlTests/graph/DiGraphTests.scala
+++ b/src/test/scala/firrtlTests/graph/DiGraphTests.scala
@@ -29,6 +29,13 @@ class DiGraphTests extends FirrtlFlatSpec {
     "c" -> Set("d"),
     "d" -> Set("a")))
 
+  val tupleGraph = DiGraph(Map(
+    ("a", 0) -> Set(("b", 2)),
+    ("a", 1) -> Set(("c", 3)),
+    ("b", 2) -> Set.empty[(String, Int)],
+    ("c", 3) -> Set.empty[(String, Int)]
+  ))
+
   val degenerateGraph = DiGraph(Map("a" -> Set.empty[String]))
 
   acyclicGraph.findSCCs.filter(_.length > 1) shouldBe empty
@@ -47,4 +54,8 @@ class DiGraphTests extends FirrtlFlatSpec {
 
   degenerateGraph.getEdgeMap should equal (degenerateGraph.reverse.getEdgeMap)
 
+  "transformNodes" should "combine vertices that collide, not drop them" in {
+    tupleGraph.transformNodes(_._1).getEdgeMap should contain ("a" -> Set("b", "c"))
+  }
+
 }