Creating custom Hamcrest matchers

In this recipe, we will create a custom Hamcrest matcher. Please refer to the previous recipe in terms of the presented assertions in the test because in the current recipe, we will combine them in our custom matchers.

Getting ready

For this recipe, our system under test will be a NewPersonGenerator class that will call an external service, NewIdentityCreator, to generate a new identity for the current person, as shown in the following code:

public class NewPersonGenerator {

    private final NewIdentityCreator newIdentityCreator;

    public NewPersonGenerator(NewIdentityCreator newIdentityCreator) {
        this.newIdentityCreator = newIdentityCreator;
    }

    public Person generateNewIdentity(Person person) {
        String newName = newIdentityCreator.createNewName(person);
        int newAge = newIdentityCreator.createNewAge(person);
        List<Person> newSiblings = newIdentityCreator.createNewSiblings(person);
        return new Person(newName...