Unit test protected method in C# using Moq

Another way in Moq to call protected member is the following template:

1. In your class, with protected member mark your function as virtual.
   For example:

   public class ClassProtected
       {
           public string CallingFunction(Customer customer)
           {
               var firstName = ProtectedFunction(customer.FirstName);
               var lastName = ProtectedFunction(customer.LastName);
   
               return string.Format("{0}, {1}", lastName, firstName);
           }
   
           protected virtual string ProtectedFunction(string value)
           {
               return value.Replace("SAP", string.Empty);
           }
       }
   

Then in your unit test add reference to

 using Moq.Protected;

and in your unit test you can write the following:

    [TestFixture]
    public class TestClassProttected
    {
        [Test]
        public void all_bad_words_should_be_scrubbed()
        {
            //Arrange
            var mockCustomerNameFormatter = new Mock<ClassProtected>();

            mockCustomerNameFormatter.Protected()
                .Setup<string>("ProtectedFunction", ItExpr.IsAny<string>())
                .Returns("here can be any value")
                .Verifiable(); // you should call this function in any case. Without calling next Verify will not give you any benefit at all

            //Act
            mockCustomerNameFormatter.Object.CallingFunction(new Customer());

            //Assert
            mockCustomerNameFormatter.Verify();
        }
    }

Take note of ItExpr. It should be used instead of It. Another gotcha awaits you at Verifiable. I don’t know why, but without calling to Verifiable Verify will not be called.