Cannot mock subclass of superclass with internal virtual methods

[GeeWee]

Unfortunately, this bug report is a little confusing, as I have tried multiple times to create a small reproducible example, but I am unable to.

I'm trying to make a mock of the Azure BlockBlobClient
This works fine, I can easily execute

var clientMock = new Mock<BlockBlobClient>();
var obj = clientMock.Object;

However, if I subclass the BlockBlobClient, everything goes wrong, even if the subclass does nothing.

[Fact]
public void ShouldBeAbleToSubclass()
{
    // Arrange
    var clientMock = new Mock<TestBlockBlobClient>();
    var obj = clientMock.Object;
}

}

public class TestBlockBlobClient : BlockBlobClient
{
}

I then get the following error:

  Error Message:
   System.ArgumentException : Type to mock must be an interface, a delegate, or a non-sealed, non-static class.
---- System.TypeLoadException : Method 'get_Pipeline' on type 'Castle.Proxies.TestBlockBlobClientProxy' from assembly 'DynamicProxyGenAssembly2, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' is overriding a method that is not visible from that assembly.
  Stack Trace:
     at Moq.CastleProxyFactory.CreateProxy(Type mockType, IInterceptor interceptor, Type[] interfaces, Object[] arguments)
   at Moq.Mock`1.InitializeInstance()
   at Moq.Mock`1.OnGetObject()
   at Moq.Mock.get_Object()
   at Moq.Mock`1.get_Object()
   at AIP.Shared.Test.BlockBlobClientTests.ShouldBeAbleToSubclass() in /home/geewee/programming/OAI/Shared.Test/BlockBlobClientTests.cs:line 91
----- Inner Stack Trace -----
   at System.Reflection.Emit.TypeBuilder.CreateTypeNoLock()
   at System.Reflection.Emit.TypeBuilder.CreateTypeInfo()
   at Castle.DynamicProxy.Generators.Emitters.AbstractTypeEmitter.CreateType(TypeBuilder type)
   at Castle.DynamicProxy.Generators.Emitters.AbstractTypeEmitter.BuildType()
   at Castle.DynamicProxy.Generators.ClassProxyGenerator.GenerateType(String name, Type[] interfaces, INamingScope namingScope)
   at Castle.DynamicProxy.Generators.ClassProxyGenerator.<>c__DisplayClass1_0.<GenerateCode>b__0(String n, INamingScope s)
   at Castle.DynamicProxy.Generators.BaseProxyGenerator.<>c__DisplayClass33_0.<ObtainProxyType>b__0(CacheKey _)
   at Castle.Core.Internal.SynchronizedDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Castle.DynamicProxy.Generators.BaseProxyGenerator.ObtainProxyType(CacheKey cacheKey, Func`3 factory)
   at Castle.DynamicProxy.Generators.ClassProxyGenerator.GenerateCode(Type[] interfaces, ProxyGenerationOptions options)
   at Castle.DynamicProxy.DefaultProxyBuilder.CreateClassProxyType(Type classToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options)
   at Castle.DynamicProxy.ProxyGenerator.CreateClassProxyType(Type classToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options)
   at Castle.DynamicProxy.ProxyGenerator.CreateClassProxy(Type classToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options, Object[] constructorArguments, IInterceptor[] interceptors)
   at Moq.CastleProxyFactory.CreateProxy(Type mockType, IInterceptor interceptor, Type[] interfaces, Object[] arguments)

It seems like Moq is trying to mock the internal virtual method Pipeline in the BlobBaseClient, which the BlockBlobClient inherits from.

Seeing as the method is internal and in another assembly, I cannot override it. However if I define a property with the same name, ala:

public class TestBlockBlobClient : BlockBlobClient
{
    public HttpPipeline Pipeline => null!;
}

I get the same error, but with the next internal virtual property

 System.TypeLoadException : Method 'get_Version' on type 'Castle.Proxies.TestBlockBlobClientProxy' from assembly 'DynamicProxyGenAssembly2, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' is overriding a method that is not visible from that assembly.

which is also a property on the superclass

So my theory is that there's something that's going on with the internal virtual properties, but only in a subclass of a subclass in another assembly.

Unfortunately, I cannot reproduce the problem, if I try to mimick the same thing locally (e.g. create two assemblies and the same internal virtual structure). I'm not sure if this is a Windsor or a Moq problem either.

[stakx]

Interesting.

I can't tell you right away why that happens, but I can tell you that the problem happens in the infrastructure below Moq, not in Moq itself. I've opened a bug report over at the DynamicProxy repository (castleproject/Core#488). I'll close your issue here, since there's nothing we can do in Moq.

P.S.: Some more info in the Castle.Core issue that might be useful to you.

[stakx]

I closed this too early... sorry. Let's close this once we've updated to a new version of DynamicProxy that contains a fix for this.

[GeeWee]

Thanks for the quick response! I see now why I couldn't reproduce it locally, as it was a little more complicated than I gave it credit for.

[smokedlinq]

Ran across this today, did anyone find a way around this or did they have to redesign the clients that are inheriting from those types of base classes?

[thackman7]

I'm running in to the same problem trying to create a mock for a named subclass of Azure DataLakeServiceClient.

Inner Exception 1:
TypeLoadException: Method 'get_ClientConfiguration' on type 'Castle.Proxies.MyAppClientProxy' from assembly 'DynamicProxyGenAssembly2, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' is overriding a method that is not visible from that assembly.

[Identekit]

I just ran into this same issue with one of my own classes.

System.TypeLoadException: Method 'MyMethod' on type 'Castle.Proxies.MyClassProxy' from assembly 'DynamicProxyGenAssembly2, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' is overriding a method that is not visible from that assembly.

This is in a .NET 6 project...I might not have made internals visible in the correct way. There's no Assembly.cs file anymore and I couldn't find much info on how to do this in .NET 6 except for the following (which may not be correct)

MyProject.csproj

<ItemGroup>
  <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
    <_Parameter1>MyProject.Test</_Parameter1>		
  </AssemblyAttribute>
</ItemGroup>

<ItemGroup>
  <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
    <_Parameter1>InternalsVisible.DynamicProxyGenAssembly2</_Parameter1>		
  </AssemblyAttribute>
</ItemGroup>

UPDATE
Turns out the problem I was having was in "InternalsVisible.DynamicProxyGenAssembly2". Once I removed the "InternalsVisible." part everything worked.

MyProject.csproj

<ItemGroup>
  <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
    <_Parameter1>MyProject.Test</_Parameter1>		
  </AssemblyAttribute>
</ItemGroup>

<ItemGroup>
  <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
    <_Parameter1>DynamicProxyGenAssembly2</_Parameter1>		
  </AssemblyAttribute>
</ItemGroup>

I also found that as of .NET 5 and higher, the following also works (source: here):

MyProject.csproj

  <ItemGroup>
	<InternalsVisibleTo Include="DynamicProxyGenAssembly2" />
  </ItemGroup>

  <ItemGroup>
    <InternalsVisibleTo Include="MyProject.Test" />
  </ItemGroup>

[gorillapower]

I have had some serious code rage with this issue. Any workarounds for when you need to create a subclass like OP has? My issue is when I try create a subclass of BlobContainerClient

[mrobinson-campion]

I'm getting the same issue when I try create a subclass of BlobServiceClient