罪魁祸首是什么？ WebApplicationFactory 的单例失败

当我调试以下代码时，我发现我注册的单例生命周期在执行到之后SqliteConnection从内部解析时并不是单例。AddDbContextGetAsync("")

我添加了以下内容来验证单例是否失败。

if (!ReferenceEquals(_sharedConnection, connection))
    throw new ApplicationException("SqliteConnection should be singleton.");

罪魁祸首是什么？解决方法是什么？完整代码如下。

正在测试的 Web API

public class AppDbContext(DbContextOptions<AppDbContext> o) : DbContext(o);

public class Program
{
    public static void Main(string[] args)
    {
        var builder = WebApplication.CreateBuilder(args);
        var app = builder.Build();

        app.MapGet("/", (AppDbContext db) => "Hello");

        app.Run();
    }
}

测试

public class CustomWebAppFactory : WebApplicationFactory<Program>
{
    private static SqliteConnection _sharedConnection = null!;

    protected override void ConfigureWebHost(IWebHostBuilder builder)
    {
        base.ConfigureWebHost(builder);

        builder.ConfigureTestServices(services =>
        {
            services.RemoveAll(typeof(SqliteConnection));
            services.RemoveAll(typeof(DbContextOptions<AppDbContext>));

            services.AddSingleton(provider =>
            {
                var connection = new SqliteConnection("DataSource=:memory:");
                return connection;
            });

            services.AddDbContext<AppDbContext>((provider, options) =>
            {
                var connection = provider.GetRequiredService<SqliteConnection>();

                if (!ReferenceEquals(_sharedConnection, connection))
                    throw new ApplicationException("SqliteConnection should be singleton.");

                options.UseSqlite(connection);
            });

            var provider = services.BuildServiceProvider();

            if (_sharedConnection != null)
                throw new ApplicationException("_sharedConnection should be null before reaching the following line.");

            _sharedConnection = provider.GetRequiredService<SqliteConnection>();
        });
    }
}

public class TrivialTest
{
    [Fact]
    public async Task Should_return_OK()
    {
        using var factory = new CustomWebAppFactory();
        using var client = factory.CreateClient();
        var response = await client.GetAsync("");
        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
    }
}