MOQ - verify exception was thrown

Question

I working with MOQ framework for my testing. I have a scenario in which I expect a fault exception to be thrown. How can I verify it was thrown?

public void          


        

Answer 1

I may be mis-reading your intent, but as far as I can see there is no need to do anything to a mock in order to test that the exception has been thrown.

It looks like you have a class with a method Foo that takes a string - lets call this InnerClass

public class InnerClass {
    public virtual void Foo(string str) {
         // do something with the string
    }
}

and a class which contains an InnerClass as a property (someProperty) which has a member Koko that takes a List as a parameter

public class OuterClass {

    private readonly InnerClass someProperty;

    public OuterClass(InnerClass someProperty) {
        this.someProperty = someProperty;
    }

    public void Koko(List list) {
         foreach (var str in list) {
              if (str != null)
                   someProperty.Foo(str);
              else
                   throw new FormatException();
          }
    } 
}

NOTE: I cannot get List to compile - tells me that the underlying type (string) must be non-nullable. AFAIK, one only needs to make value types nullable, reference types are implicitly nullable.

It looks like you want to test that if you pass in a list of strings where any of them are null that a FormatException is thrown.

If so, then the only reason for a MOQ is to release us from worrying about the InnerClass functionality. Foo is a method, so, unless we are using strict mocks, we can just create an InnerClass mock with no other setup.

There is an attribute [ExpectedException] with which we can tag our test to verify that the exception has been thrown.

[TestMethod]
[ExpectedException(typeof(FormatException))]
public void ExceptionThrown() {

    var list = new List() {
        "Abel",
        "Baker",
        null,
        "Charlie"
    };

    var outer = new OuterClass(new Mock().Object);
    outer.Koko(list);

}

This test will pass if a FormatException is thrown and fail if it is not.