public void Crossover()
        {
            var chars = CharSeq.Of("a-zA-Z");

            var g1 = new CharacterChromosome(chars, 20).ToSeq();
            var g2 = new CharacterChromosome(chars, 20).ToSeq();

            const int rv1 = 12;

            RandomRegistry.Using(new ConstRandom(rv1), r =>
            {
                var crossover = new SinglePointCrossover <CharacterGene, double>();

                var g1C = MutableSeq.Of <CharacterGene>(g1);
                var g2C = MutableSeq.Of <CharacterGene>(g2);
                crossover.Crossover(g1C, g2C);

                Assert.Equal(g1C.ToImmutableSeq().SubSeq(0, rv1), g1.SubSeq(0, rv1));
                Assert.Equal(g1C.SubSeq(rv1), g2.SubSeq(rv1));
                Assert.NotEqual(g1C, g2);
                Assert.NotEqual(g2C, g1);

                const int rv2 = 0;
                RandomRegistry.Using(new ConstRandom(rv2), r2 =>
                {
                    var g1C2 = MutableSeq.Of <CharacterGene>(g1);
                    var g2C2 = MutableSeq.Of <CharacterGene>(g2);
                    crossover.Crossover(g1C2, g2C2);
                    Assert.Equal(g1C2, g2);
                    Assert.Equal(g2C2, g1);
                    Assert.Equal(g1C2.SubSeq(0, rv2), g1.SubSeq(0, rv2));
                    Assert.Equal(g1C2.SubSeq(rv2), g2.SubSeq(rv2));

                    const int rv3 = 1;
                    RandomRegistry.Using(new ConstRandom(rv3), r3 =>
                    {
                        var g1C3 = MutableSeq.Of <CharacterGene>(g1);
                        var g2C3 = MutableSeq.Of <CharacterGene>(g2);
                        crossover.Crossover(g1C3, g2C3);
                        Assert.Equal(g1C3.SubSeq(0, rv3), g1.SubSeq(0, rv3));
                        Assert.Equal(g1C3.SubSeq(rv3), g2.SubSeq(rv3));

                        var rv4 = g1.Length;
                        RandomRegistry.Using(new ConstRandom(rv4), r4 =>
                        {
                            var g1C4 = MutableSeq.Of <CharacterGene>(g1);
                            var g2C4 = MutableSeq.Of <CharacterGene>(g2);
                            crossover.Crossover(g1C4, g2C);
                            Assert.Equal(g1C4, g1);
                            Assert.Equal(g2C4, g2);
                            Assert.Equal(g1C4.SubSeq(0, rv4), g1.SubSeq(0, rv4));
                            Assert.Equal(g1C4.SubSeq(rv4), g2.SubSeq(rv4));
                        });
                    });
                });
            });
        }