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));
}
