Why am I getting an Exception with the message Invalid setup on a non-virtual overridable in VB member

Question

I have a unit test where I have to mock a non-virtual method that returns a bool type  public class XmlCupboardAccess       public bool IsDataEntityInXmlCupboard string dataId                                            out string nameInCupboard                                            out string refTypeInCupboard                                            string nameTemplate   null                return IsDataEntityInXmlCupboard  theDb  dataId  out nameInCupboard  out refTypeInCupboard  nameTemplate             So I have a mock object of XmlCupboardAccess class and I am trying to setup mock for this method in my test case as shown below   TestMethod  Public void Test         private string temp1      private string temp2      private Mock lt XmlCupboardAccess gt   xmlCupboardAccess   new Mock lt XmlCupboardAccess gt          xmlCupboardAccess Setup x   gt  x IsDataEntityInXmlCupboard It IsAny lt string gt     out temp1  out temp2  It IsAny lt string gt      Returns false          exception is thrown by this line of code     But this line throws exception   Invalid setup on a non-virtual  overridable in VB  member   x   gt  x IsDataEntityInXmlCupboard It IsAny lt String gt      temp1   temp2   It IsAny lt String gt       Any suggestion how to get around this exception

User · Answer

Instead of mocking concrete class you should mock that class interface. Extract interface from XmlCupboardAccess class

public interface IXmlCupboardAccess
{
    bool IsDataEntityInXmlCupboard(string dataId, out string nameInCupboard, out string refTypeInCupboard, string nameTemplate = null);
}

And instead of

private Mock<XmlCupboardAccess> _xmlCupboardAccess = new Mock<XmlCupboardAccess>();

change to

private Mock<IXmlCupboardAccess> _xmlCupboardAccess = new Mock<IXmlCupboardAccess>();

User · Answer

As help to anybody that had the same problem as me  I accidentally mistyped the implementation type instead of the interface e g   var mockFileBrowser   new Mock lt FileBrowser gt       instead of  var mockFileBrowser   new Mock lt IFileBrowser gt

User · Answer

Moq cannot mock non-virtual methods and sealed classes  While running a test using mock object  MOQ actually creates an in-memory proxy type which inherits from your  XmlCupboardAccess  and overrides the behaviors that you have set up in the  SetUp  method  And as you know in C   you can override something only if it is marked as virtual which isn t the case with Java  Java assumes every non-static method to be virtual by default   Another thing I believe you should consider is introducing an interface for your  CupboardAccess  and start mocking the interface instead  It would help you decouple your code  and have benefits in the longer run   Lastly  there are frameworks like   TypeMock and JustMock which work directly with the IL and hence can mock non-virtual methods  Both however  are commercial products

User · Answer

Code    private static void RegisterServices IKernel kernel        Mock lt IProductRepository gt  mock new Mock lt IProductRepository gt         mock Setup x   gt  x Products  Returns new List lt Product gt                new Product  Name    Football   Price   23           new Product  Name    Surf board   Price   179           new Product  Name    Running shose   Price   95               kernel Bind lt IProductRepository gt    ToConstant mock Object               but see exception

User · Answer

You ll get this error as well if you are verifying that an extension method of an interface is called   For example if you are mocking   var mockValidator   new Mock lt IValidator lt Foo gt  gt     mockValidator    Verify validator   gt  validator ValidateAndThrow foo  null      You will get the same exception because  ValidateAndThrow   is an extension on the IValidator lt T gt  interface   public static void ValidateAndThrow lt T gt  this IValidator lt T gt  validator  T instance  string ruleSet   null

User · Answer

Please see Why does the property I want to mock need to be virtual   You may have to write a wrapper interface or mark the property as virtual abstract as Moq creates a proxy class that it uses to intercept calls and return your custom values that you put in the  Returns x  call

[c#] Why am I getting an Exception with the message "Invalid setup on a non-virtual (overridable in VB) member..."?

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