public void Test <T>(Arithmetics <T> a)
where T : notnull
{
var one = a.One;
var two = a.Mul(one, 2L);
a.Mul(one, 2d).Should().Be(two);
var eleven = a.Mul(one, 11L);
var four = a.Mul(one, 4L);
var d = a.DivRem(eleven, four, out var r);
d.Should().Be(2);
r.Should().Be(a.Mul(one, 3L));
a.Mod(eleven, four).Should().Be(a.Mul(one, 3L));
var nEleven = a.Negative(eleven);
d = a.DivNonNegativeRem(nEleven, four, out r);
d.Should().Be(-3);
r.Should().Be(one);
a.Mod(nEleven, four).Should().Be(one);
}