Fix bug in DiGraph.reverse on an graph with one vertex, no edges (#628)

1 files changed, 12 insertions, 0 deletions

diff --git a/src/test/scala/firrtlTests/graph/DiGraphTests.scala b/src/test/scala/firrtlTests/graph/DiGraphTests.scala
index 6546e147..9eb1c7f8 100644
--- a/src/test/scala/firrtlTests/graph/DiGraphTests.scala
+++ b/src/test/scala/firrtlTests/graph/DiGraphTests.scala
@@ -16,12 +16,20 @@ class DiGraphTests extends FirrtlFlatSpec {
     "d" -> Set("e"),
     "e" -> Set.empty[String]))
 
+  val reversedAcyclicGraph = DiGraph(Map(
+    "a" -> Set.empty[String],
+    "b" -> Set("a"),
+    "c" -> Set("a"),
+    "d" -> Set("b", "c"),
+    "e" -> Set("d")))
+
   val cyclicGraph = DiGraph(Map(
     "a" -> Set("b","c"),
     "b" -> Set("d"),
     "c" -> Set("d"),
     "d" -> Set("a")))
 
+  val degenerateGraph = DiGraph(Map("a" -> Set.empty[String]))
 
   acyclicGraph.findSCCs.filter(_.length > 1) shouldBe empty
 
@@ -35,4 +43,8 @@ class DiGraphTests extends FirrtlFlatSpec {
 
   a [cyclicGraph.CyclicException] should be thrownBy cyclicGraph.linearize
 
+  acyclicGraph.reverse.edges should equal (reversedAcyclicGraph.edges)
+
+  degenerateGraph.edges should equal (degenerateGraph.reverse.edges)
+
 }