EF6 error when using in-memory testing

Question

Mocked setup below (the GenerateTrades() and other methods in ContextFactory are just returning a List AsQueryable with sample data):

_trades = ContextFactory.GenerateTrades();
_hedges = ContextFactory.GenerateHedges();
_exposures = ContextFactory.GenerateExposures();

_ctx = new Mock<FxContext>();

var fakeTrades = new Mock<DbSet<Trade>>();
fakeTrades.As<IQueryable<Trade>>().Setup(m => m.Provider).Returns(_trades.Provider);
fakeTrades.As<IQueryable<Trade>>().Setup(m => m.Expression).Returns(_trades.Expression);
fakeTrades.As<IQueryable<Trade>>().Setup(m => m.ElementType).Returns(_trades.ElementType);
fakeTrades.As<IQueryable<Trade>>().Setup(m => m.GetEnumerator()).Returns(_trades.GetEnumerator());

var fakeHedges = new Mock<DbSet<Hedge>>();
fakeHedges.As<IQueryable<Hedge>>().Setup(m => m.Provider).Returns(_hedges.Provider);
fakeHedges.As<IQueryable<Hedge>>().Setup(m => m.Expression).Returns(_hedges.Expression);
fakeHedges.As<IQueryable<Hedge>>().Setup(m => m.ElementType).Returns(_hedges.ElementType);
fakeHedges.As<IQueryable<Hedge>>().Setup(m => m.GetEnumerator()).Returns(_hedges.GetEnumerator());

var fakeExposures = new Mock<DbSet<Exposure>>();
fakeExposures.As<IQueryable<Exposure>>().Setup(m => m.Provider).Returns(_exposures.Provider);
fakeExposures.As<IQueryable<Exposure>>().Setup(m => m.Expression).Returns(_exposures.Expression);
fakeExposures.As<IQueryable<Exposure>>().Setup(m => m.ElementType).Returns(_exposures.ElementType);
fakeExposures.As<IQueryable<Exposure>>().Setup(m => m.GetEnumerator()).Returns(_exposures.GetEnumerator());

_ctx.Setup(c => c.Trades).Returns(fakeTrades.Object);
_ctx.Setup(c => c.Hedges).Returns(fakeHedges.Object);
_ctx.Setup(c => c.Exposures).Returns(fakeExposures.Object);    

Part of test code looks like:

_sut = (from x in _ctx.Object.Hedges
       where x.Id == ContextFactory.s_hedge01Id
       select x).FirstOrDefault();
_ctx.Object.Hedges.Attach(_sut);
_ctx.Object.Entry(_sut).Collection(x => x.HedgedTrades).Load();  

On the last line I get an exception:

{"Member 'Load' cannot be called for property 'HedgedTrades' because the entity of type 'Hedge' does not exist in the context. To add an entity to the context call the Add or Attach method of DbSet<Hedge>."}

I have verified that in fact the _sut Hedge is actually an instance of a Hedge (not null or a stub) and as the code seems to indicate, I have attached the Hedge to the context explicitly (though I would think the query should bring the object into the context automagically). Am I missing something?

Answer 1

It seems like here in your test you are mixing two separate approaches. Error you received states that you are trying to access DbContext inherited logic, but it is mocked. If you want to perform your unit tests against database with use of FxContext then do not mock it. If you want test other part of software then you should mock interface that FxContext should implement. This will enable you to fullfil dependency injection principle in your code which will help you then organize your test in more predictable way.