Why is this Autofac mock's lifetime disposed in a simple MSpec test? -

i've got base class i'm using mspec provides convenience methods around automock:

public abstract class subjectbuildercontext {     static automock _container;      protected static isubjectbuilderconfigurationcontext<t> buildsubject<t>()     {         _container = automock.getloose();         return new subjectbuilderconfigurationcontext<t>(_container);     }      protected static mock<tdouble> getmock<tdouble>()          tdouble : class     {         return _container.mock<tdouble>();     } } 

occasionally, i'm seeing exception happen when attempting retrieve mock so:

it should_store_the_receipt = () => getmock<ifileservice>().verify(f => f.savefileasync(moq.it.isany<byte[]>(), moq.it.isany<string>()), times.once()); 

here's exception:

system.objectdisposedexceptioninstances cannot resolved , nested lifetimes cannot created lifetimescope has been disposed.

i'm guessing has way mspec runs tests (via reflection) , there's period of time when nothing actively has references of objects in underlying lifetime scope being used automock causes lifetimescope disposed. what's going on here, , there simple way me keep happening?

the automock lifetime scope autofac.extras.moq disposed when mock disposed. if you're getting this, means automock instance has been disposed or has otherwise lost scope , gc has cleaned up.

given that, there few possibilities.

the first possibility you've got potential threading challenges around async method calls. looking @ method that's being mocked, see you're verifying call savefileasync method. however, don't see async related code in there, , i'm not entirely sure when/how tests running calling given posted code, if there situation async call causes test run on 1 thread while automock loses scope or otherwise gets killed on other thread, see happening.

the second possibility the mix of static , instance items in context. storing automock static, appears context class in resides base class intended supply instance-related values. if 2 tests run in parallel, example, first test set automock thinks needs, second test overwrite automock , first go out of scope, disposing scope.

the third possibility multiple calls buildsubject<t> in 1 test. call buildsubject<t> initializes automock. if call multiple times in 1 test, despite changing t type, you'll stomping automock each time , associated lifetime scope disposed.

the fourth possibility a test ordering problem. if see not other times, tests inadvertently assume setup, call buildsubject<t>, has been done; while other tests may not make assumption , call buildsubject<t> themselves. depending on order tests run, may lucky , not see exception, other times may run problem buildsubject<t> gets called @ wrong time , causes pain.