I'm trying to write a unit test of a repository implementation. The repository uses RavenDB as a database. For the unit tests, I would like to mock the RavenDB parts. In order to create the mocks (fakes) I'm using FakeItEasy. I figured there wouldn't be any problems with the mocking/faking since the RavenDB API is accessed through interfaces.
I do however have a problem when trying to instantiate a specific mock. The relevant parts of my unit test code looks like this:
[Fact]
public void Test() {
UserDocument doc = ...;
IQueryable<UserDocument> where = A.Fake<IQueryable<UserDocument>>();
A.CallTo(() => where.First()).Returns(doc);
IRavenQueryable<UserDocument> query = A.Fake<IRavenQueryable<UserDocument>>();
IDocumentSession session = A.Fake<IDocumentSession>();
A.CallTo(() => session.Query<UserDocument>()).Returns(query);
IDocumentStore store = A.Fake<IDocumentStore>();
A.CallTo(() => store.OpenSession()).Returns(session);
.
.
.
}
When instantiating the IRavenQueryable fake I get an exception. This is the log from the Xunit.net runner:
UnitTest.Test : FakeItEasy.Core.FakeCreationException :
Failed to create fake of type "System.Linq.IQueryable`1[UserDocument]".
Below is a list of reasons for failure per attempted constructor:
No constructor arguments failed:
No default constructor was found on the type System.Linq.IQueryable`1[UserDocument].
Stack Trace:
vid FakeItEasy.Core.DefaultExceptionThrower.ThrowFailedToGenerateProxyWithResolvedConstructors(Type typeOfFake, String reasonForFailureOfUnspecifiedConstructor, IEnumerable`1 resolvedConstructors)
vid FakeItEasy.Creation.FakeObjectCreator.TryCreateFakeWithDummyArgumentsForConstructor(Type typeOfFake, FakeOptions fakeOptions, IDummyValueCreationSession session, String failReasonForDefaultConstructor, Boolean throwOnFailure)
vid FakeItEasy.Creation.FakeObjectCreator.CreateFake(Type typeOfFake, FakeOptions fakeOptions, IDummyValueCreationSession session, Boolean throwOnFailure)
vid FakeItEasy.Creation.DefaultFakeAndDummyManager.CreateFake(Type typeOfFake, FakeOptions options)
vid FakeItEasy.Creation.DefaultFakeCreatorFacade.CreateFake[T](Action`1 options)
The "no default constructor found" doesn't make any sense since what I'm trying to fake is an interface. Does anyone have a suggestion what the problem might be?
IRavenQueryable<T>. Are you sure the exception isn't occurring when you instantiate theIQueryable<UserDocument>? – Honna