public void SelectsConversion()
        {
            var spec = new IntegerGreaterThanZero();
            var converter = (Expression<Func<double, int>>)(d => Math.Sign(d));
            var convertedSpec = new Conversion<double, int>(spec, converter);

            Assert.That(convertedSpec.IsSatisfiedBy(1), Is.True);
            Assert.That(convertedSpec.IsSatisfiedBy(0), Is.False);
            Assert.That(convertedSpec.IsSatisfiedBy(-1), Is.False);
        }