Stubbing methods so that they throw exceptions

In this recipe, we will stub a method that returns a value so that it throws an exception. Since we want our code to be beautiful, we'll use the catch-exception library to catch and check the exceptions thrown in our system.

Getting ready

Ensure that you have the catch-exception library on your classpath; refer to the Stubbing methods so that they throw exceptions recipe of Chapter 4, Stubbing Behavior of Mocks, for details on how to add catch-exception to your project.

This recipe will reuse the example from the previous recipe. We have a class that calculates an average value of tax factors (AverageTaxFactorCalculator) and TaxFactorFetcher is the provider of those values. One of the values is picked from the database (and we'll stub that method). We will test those two classes as a unit. For your convenience (so that you don't scroll around the book too much), I'm showing you the classes here (don't worry, they're really small):

public class AverageTaxFactorCalculator...