result.addItem(2, 0, d);
assertEquals("Test if sets are equal", result, set.closure());
// ---- Case 2 ----
Terminal a = new Terminal("a");
Terminal b = new Terminal("b");
Terminal c = new Terminal("c");
Nonterminal A = new Nonterminal("A");
Nonterminal B = new Nonterminal("B");
Nonterminal C = new Nonterminal("C");
Nonterminal D = new Nonterminal("D");