How can you mock a method that returns an interface?

Question

I need to mock a method that returns an interface and I can't figure it out. This was my try. I don't know how what to return, as you can not return an interface.

        messagingClient.Setup(x =>
             x.CreateMessage(new OrganizationUserDeletedDomainEvent
             {
                 UserType = 1,
                 OrganizationUserId = 1,
                 OrganizationId = 1,
                 DeletedAt = 100000
             })).Returns();

The method has this signature:

IMessage<TContent> CreateMessage<TContent>(TContent messageContent)
   where TContent : class, new();

Answer 1

you can create a mock of IMessage and use this mock to be returned

var messageMock = new Mock<IMessage<OrganizationUserDeletedDomainEvent>>();

messagingClient.Setup(x =>
     x.CreateMessage(new OrganizationUserDeletedDomainEvent
     {
         UserType = 1,
         OrganizationUserId = 1,
         OrganizationId = 1,
         DeletedAt = 100000
     })).Returns(messageMock.Object);