We are using EF Core with Sqlite to test the database of our app. However we are unable to store any entities in the DB tables.
Sample program:

using Microsoft.EntityFrameworkCore;
  using Microsoft.Extensions.DependencyInjection;
  using Microsoft.Extensions.Logging;

  namespace ConsoleApp5;

  class Program
  {
    static void Main(string[] args)
    {
        var sc = new ServiceCollection();

        ILoggerFactory loggerFactory = LoggerFactory.Create(builder => builder.AddConsole());
        ILogger logger = loggerFactory.CreateLogger<Program>();

        sc.AddDbContext<Context>(options =>
            options
                .UseSqlite("Data Source=:memory:")
                .EnableDetailedErrors()
                .UseLoggerFactory(loggerFactory)
            );

        var services = sc.BuildServiceProvider();
        
        using var scope = services.CreateScope();

        var dbContext = scope.ServiceProvider.GetRequiredService<Context>();

        dbContext.Database.EnsureCreated();
        try
        {
            var myA = new A();

            dbContext.As.Add(myA);
            dbContext.SaveChanges();

            var x = dbContext.As.Find(myA.Id);

            Console.WriteLine( myA.Id);

        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
        Console.ReadKey();
    }
  }

  public class Context(DbContextOptions<Context> options) : DbContext(options)
  {
    public DbSet<A> As { get; set; }


    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        A.OnModelCreating(modelBuilder);
    }
  };

  public abstract class Entity
  {

    public string Id { get; set; } = Guid.NewGuid().ToString();
  }

  public class A : Entity
  {
      internal static void OnModelCreating(ModelBuilder modelBuilder)
      {
      }
  }

this results in the following logging, table is created, but insert fails:

info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (12ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
      SELECT COUNT(*) FROM "sqlite_master" WHERE "type" = 'table' AND "rootpage" IS NOT NULL;
info: Microsoft.EntityFrameworkCore.Database.Command[20101]
      Executed DbCommand (1ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
      CREATE TABLE "As" (
          "Id" TEXT NOT NULL CONSTRAINT "PK_As" PRIMARY KEY
      );
fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
      Failed executing DbCommand (3ms) [Parameters=[@p0='?' (Size = 36)], CommandType='Text', CommandTimeout='30']
      INSERT INTO "As" ("Id")
      VALUES (@p0);
fail: Microsoft.EntityFrameworkCore.Update[10000]
      An exception occurred in the database while saving changes for context type 'ConsoleApp5.Context'.
      Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while saving the entity changes. See the inner exception for details.
       ---> Microsoft.Data.Sqlite.SqliteException (0x80004005): SQLite Error 1: 'no such table: As'.

What are we doing wrong?