public void TestParsing05() {
var g = new Grammar(new List<Production>{
CFGParser.Production("<X_0> → <X_1>"),
CFGParser.Production("<X_1> → ε"),
CFGParser.Production("<X_1> → 'x2' <X_0> <X_0> 'x1'"),
CFGParser.Production("<X_1> → <X_0>"),
}, Nonterminal.Of("X_0"));
var sentences = new List<Sentence>();
sentences.Add(Sentence.FromWords("x2 x1"));
ExecuteTest(g, sentences);
}