@Test public void test_Aaubu_Acudu() { // au,bu + cu,du -> [a,b,c,d]->[u,u,u,u]
SingletonPredictionContext a = createSingleton(u(), 1);
SingletonPredictionContext b = createSingleton(u(), 2);
SingletonPredictionContext c = createSingleton(u(), 3);
SingletonPredictionContext d = createSingleton(u(), 4);
ArrayPredictionContext A1 = array(a, b);
ArrayPredictionContext A2 = array(c, d);
PredictionContext r = PredictionContext.merge(A1, A2, rootIsWildcard(), null);
System.out.println(toDOTString(r, rootIsWildcard()));
String expecting =
"digraph G {\n" +
"rankdir=LR;\n" +