Mocking using Moq in c#

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Classic example which demonstrates that if you cannot unit test a particular component, REFACTOR it!

This is why I love what any mocking framework enforces you to do – write decoupled code.

In your example, the ProductBusiness class is tightly coupled with the ProductDataAccess class. You could decouple it using (like most of the answers suggest) dependency injection. By doing so, you would end up depending on the IProductDataAccess abstraction and not on any concrete implementation of it.

Another point to note, when you are writing tests/specifications for the business layer, you would typically want to test the “behavior” and not the “state”. So, although you could have asserts that verify if “true” was returned, your tests should really test if the expected data access calls that were set using MOQ were actually executed using the .Verify API of MOQ.

Try adding behavior tests where you expect an exception to be thrown (using the “.Throws” API) by the data access layer and check if you need any special handling at the business layer.

Like Kevin suggests, the following implementation of ProductBusiness will work:

public class ProductBusiness
{
  private readonly IProductDataAccess  _productDataAccess;

  public ProductBusiness(IProductDataAccess productDataAccess)
  {
      _productDataAccess = productDataAccess;
  }

  public bool CreateProduct(Product newProduct)
  {
    bool result=_productDataAccess.CreateProduct(newProduct);
    return result;
  }
}

and use any xunit testing framework to write the test as: 

 var mockDataAccess = new Mock<IProductDataAccess>();
 mockDataAccess.Setup(m => m.CreateProduct(It.IsAny<Product>())).Returns(true);
 var productBusiness = new ProductBusiness(mockDataAccess.Object);
 //behavior to be tested

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