public void TestMultiOperatorFormula1()
        {
            Conjunction conj = new Conjunction(new Negation(C),
                                               B);
            BooleanExpression formula = new Disjunction(new Negation(new Disjunction(new Negation(A), B)),
                                                        conj);
            BooleanExpression actual = formula.ToDNF();

            BooleanExpression expected = new Disjunction(new Conjunction(A, new Negation(B)),
                                                         new Conjunction(new Negation(C), B));

            Assert.True(actual.Is_DNF());
            Assert.True(expected.Is_DNF());
            Assert.Equal(expected, actual);
        }