diff --git a/transport/routing_test.go b/transport/routing_test.go
new file mode 100644
index 00000000..9485577b
--- /dev/null
+++ b/transport/routing_test.go
@@ -0,0 +1,27 @@
+package transport
+
+import "testing"
+
+func TestShardPortIterator(t *testing.T) {
+	t.Parallel()
+	for shards := 1; shards < 128; shards++ {
+		for shard := 0; shard < shards; shard++ {
+			si := ShardInfo{
+				Shard:    uint16(shard),
+				NrShards: uint16(shards),
+			}
+
+			it := ShardPortIterator(si)
+			finishPort := it()
+			for port := it(); port != finishPort; port = it() {
+				if port < minPort || port > maxPort {
+					t.Fatalf("port %d is not in range [%d, %d]", port, minPort, maxPort)
+				}
+
+				if int(port)%shards != shard {
+					t.Fatalf("port %d doesn't correspond to shard %d", port, shard)
+				}
+			}
+		}
+	}
+}