add failing test

Author: alixander

e2etests/regression_test.go

@@ -58,6 +58,17 @@ d: {
   shape: step
 }
 c -> d
+`,
+		},
+		{
+			name: "class_span_sequence",
+			script: `shape: sequence_diagram
+a: { shape: class }
+b
+
+group: {
+  a.t -> b.t
+}
 `,
 		},
 		{