public void TestParsing13() {
var g = new Grammar(new List<Production>{
CFGParser.Production("<S> → <A>"),
CFGParser.Production("<A> → <A> 'x' <A>"),
CFGParser.Production("<A> → ε")
}, Nonterminal.Of("S"));
var sentences = new List<Sentence>();
sentences.Add(Sentence.FromWords("x x"));
ExecuteTest(g, sentences);
}