Stubbing methods that return values

In this recipe, we will stub a method that returns a value so that it returns our desired result.

Getting ready

For this recipe, our system under test will be MeanTaxFactorCalculator, which calls TaxFactorFetcher twice to get a tax factor for the given person and then calculates a mean value for those two results as follows:

public class MeanTaxFactorCalculator {

    private final TaxFactorFetcher taxFactorFetcher;

    public MeanTaxFactorCalculator(TaxFactorFetcher taxFactorFetcher) {
        this.taxFactorFetcher = taxFactorFetcher;
    }

    public double calculateMeanTaxFactorFor(Person person) {
        double taxFactor = taxFactorFetcher.getTaxFactorFor(person);
        double anotherTaxFactor = taxFactorFetcher.getTaxFactorFor(person);
        return (taxFactor + anotherTaxFactor) / 2;
    }

}

How to do it...

To stub nonvoid methods so they return a given value, you have to perform the following steps:

1. For the BDD approach, call BDDMockito.given(mock...