public void FlipSign(string value, bool isPositive) { Sign sign = new Sign(value); string expectedLabel = isPositive ? string.Empty : "-"; Assert.That(sign.IsPositive(), Is.EqualTo(!isPositive)); Assert.That(sign.IsNegative(), Is.Not.EqualTo(!isPositive)); sign.FlipSign(); Assert.That(sign.IsPositive(), Is.EqualTo(isPositive)); Assert.That(sign.IsNegative(), Is.Not.EqualTo(isPositive)); Assert.That(sign.Label(), Is.EqualTo(expectedLabel)); }