Справочник по ASP.NET — 4. Тестирование

public class CustomWebApplicationFactory<TProgram> : WebApplicationFactory<TProgram> where TProgram : class
{
    protected override void ConfigureWebHost(IWebHostBuilder builder)
    {
        builder.ConfigureServices(services =>
        {
            // Замена реальных сервисов на моки
            var descriptor = services.SingleOrDefault(d => d.ServiceType == typeof(DbContextOptions<AppDbContext>));
            if (descriptor != null)
                services.Remove(descriptor);

            services.AddDbContext<AppDbContext>(options =>
                options.UseInMemoryDatabase("TestDb"));
        });
    }
}