public void Selection() { var criteria = (Expression<Func<int, bool>>)(x => x > 0); var negatedSpec = new Proposition<int>(criteria); Assert.That(negatedSpec.IsSatisfiedBy(1), Is.True); Assert.That(negatedSpec.IsSatisfiedBy(0), Is.False); Assert.That(negatedSpec.IsSatisfiedBy(-1), Is.False); }