InMemoryDatabase auto increment with initial seed

[lcssanches]

Auto increment/Identity initial value is not correct when the table has seeds

Steps to reproduce

Create a table with Identity Column Id

class CorConfig : IEntityTypeConfiguration<Cor>
{
        public void Configure(EntityTypeBuilder<Cor> builder)
        {
            builder.ToTable("Cores");
            builder.HasKey(r => r.Id).UseMySqlIdentityColumn();
            builder.Property(r => r.Nome).IsRequired().HasMaxLength(255);
            builder.Property(v => v.RGB).IsRequired().HasMaxLength(7);

            builder.HasData(GetSeed());
        }

        private ICollection<Cor> GetSeed()
        {
            return new List<Cor>()
            {
                new Cor(){Id=1, Nome="Black", RGB="#000"},
                new Cor(){Id=2, Nome="White", RGB="#fff"},
            };
        }
}

Create a test:
I comment query.Handler because just to simplify things, in fact it will execute DbSet.Add()

        [Test]
        public async Task CreateCorCommandHandlerTest()
        {
            var Context = CBERPContextFactory.Create();

            /*var query = new CreateCorCommandHandler(Context);
            var command = new CreateCorCommand();
            command.Nome = "123123";
            command.RGB = "#001122";
            var colecaoId = await query.Handle(command, CancellationToken.None);*/

            var cor = new Domain.Entities.Cor() { Nome = "Gray", RGB = "#CCC" };
            Context.Cores.Add(cor);
            await Context.SaveChangesAsync();
            var dbCor = Context.Cores.Where(p => p.Id == cor.Id).SingleOrDefault();
            CBERPContextFactory.Destroy(Context);
            var colecaoId = cor.Id;

            //Assert
            Assert.IsInstanceOf<long>(colecaoId);
            Assert.NotZero(colecaoId);                       
            Assert.NotNull(dbCor);
            Assert.AreEqual(cor.Nome, dbCor.Nome);
            Assert.AreEqual(cor.RGB, dbCor.RGB);
        }

I expect this test to pass, but instead, I receive the following exception
Message: System.ArgumentException : An item with the same key has already been added. Key: 1

If I change the table to be empty by default, and change the test to add more than one entity on database, the auto increment work as expected, resulting in IDs 1 and 2.

Further technical details

EF Core version: 2.2.4
Database Provider: Microsoft.EntityFrameworkCore.InMemory 2.2.4
Operating system: Windows 10
IDE: (e.g. Visual Studio 2017 15.4) VS2019

[ajcvickers]

Duplicate of #6872

[emilborowiec]

This bug is still occurring in preview 5 of EF Core 3.0.

I actually don't think it is a duplicate of #6872 which seems to be more about resetting value generator between the tests. Here the problem is that value generator does not take into account explicit IDs passed in HasData calls and tries to start from 1 for integers.

Please consider reopening.