VS单元测试"未能加载文件或程序集,或它的某一个依赖项"

Autofac.Core.DependencyResolutionException : An error occurred during the activation of a particular registration. See the inner exception for details. Registration: Activator = Object (DelegateActivator), Services = [某接口名.Api], Lifetime = Autofac.Core.Lifetime.CurrentScopeLifetime, Sharing = Shared, Ownership = OwnedByLifetimeScope ---> 未能加载文件或程序集“Autofac, Version=Autofac.Core.DependencyResolutionException : An