GetMock<DbSet<MyClass>>() throws TargetInvocationException (EntityFrameworkCore)

[demauk]

Hi,

This code was working on dotnet Core 3.1, AutoMocker 2.0.1:
var mockSet = mocker.GetMock<DbSet<MyClass>>();
DbSet<T> is declared in Microsoft.EntityFrameworkCore.

That line doesn't work in later versions of AutoMocker. They throw the following exception:

  Message: 
    System.Reflection.TargetInvocationException : Exception has been thrown by the target of an invocation.
      ----> System.ArgumentNullException : Value cannot be null. (Parameter 'type')
  Stack Trace: 
    RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
    RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
    RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
    Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
    ProxyGenerator.CreateClassProxyInstance(Type proxyType, List`1 proxyArguments, Type classToProxy, Object[] constructorArguments)
    ProxyGenerator.CreateClassProxy(Type classToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options, Object[] constructorArguments, IInterceptor[] interceptors)
    CastleProxyFactory.CreateProxy(Type mockType, IInterceptor interceptor, Type[] interfaces, Object[] arguments) line 56
    Mock`1.InitializeInstance() line 322
    Mock`1.OnGetObject() line 340
    Mock.get_Object() line 182
    Mock`1.get_Object() line 294
    GetMyFileProcessorTests.Setup() line 43
    --ArgumentNullException
    IntrospectionExtensions.GetTypeInfo(Type type)
    DbContext.ctor(DbContextOptions options)
    SurrogateContext.ctor(DbContextOptions`1 options) line 11
    SurrogateContextProxy.ctor(IInterceptor[] , DbContextOptions`1 options)

Checking out other issues, I saw the enablePrivate: true argument and gave that a try in v2.3, just in case. But it didn't help.

Is there a workaround?

Thanks!

[Keboo]

@demauk can you give this code a try:

var mock = new Mock<DbSet<MyClass>>();

var value = mock.Object;

From your stack trace it appears that the difference may be in the version of Moq, that is being used, not directly in this library.

[adamhewitt627]

I reproduced this in 2.3, but enablePrivate works. Can you check that again, and perhaps see if you can provide a reproduction where it still fails?

[demauk]

Apologies!

GetMock<DbSet<MyClass>>(true) does work. The problem was that enablePrivate: true exposed another error further down my Setup() and I assumed it was the same exception.

But this time, replacing x = mocker.GetMock with x = new Mock followed by mocker.Use(x) did the trick.

[adamhewitt627]

I'm hoping we have that fix in place soon so you don't have to specify the argument or call Use.