Dummy repository implementation

DummyRepository.cs

public interface IRepository<TEntity, in TId>
        where TEntity : IEntity<TId>
    {
        Task<TEntity> GetById(TId id);
        Task Insert(TEntity entity);
        Task Update(TEntity entity);
        Task Remove(TId id);
    }

    public interface IEntity<TId>
    {
        TId Id { get; set; }
    }

    public abstract class RepositoryBase<TEntity, TId>: IRepository<TEntity, TId>
        where TEntity : class, IEntity<TId>, new()
        where TId: struct
    {
        private readonly IShopContext shopContext;

        protected RepositoryBase(IShopContext shopContext)
        {
            this.shopContext = shopContext;
        }

        public async virtual Task<TEntity> GetById(TId id)
        {
            return await shopContext.Set<TEntity>().FindAsync(id);
        }

        public async virtual Task Insert(TEntity entity)
        {
            await shopContext.Set<TEntity>().AddAsync(entity);
            await shopContext.SaveChangesAsync();
        }

        public async virtual Task Update(TEntity entity)
        {
            shopContext.Set<TEntity>().Update(entity);
            await shopContext.SaveChangesAsync();
        }

        public async virtual Task Remove(TId id)
        {
            var entity = new TEntity() { Id = id};
            shopContext.Attach(entity);
            shopContext.Remove(entity);
            await shopContext.SaveChangesAsync();
        }
    }

    public class CategoryRepository : RepositoryBase<Category, int>
    {
        public CategoryRepository(IShopContext shopContext) : base(shopContext)
        {
        }
    }