JUnit Hamcrest assertion

Question

Is there a Hamcrest Matcher that cleanly lets me assert that the result of a method, that returns a Collection of objects, has at least one object that contains a property with certain value?

For example:

class Person {
   private String name;
}

The method under test returns a collection of Person. I need to assert that at least one Person is called Peter.

Answer 1

First, you need to create a Matcher that can match a Person's name. Then, you could use hamcrest's CoreMatchers#hasItem to check if a Collection has an item this mathcer matches.

Personally, I like to declare such matchers anonymously in static methods as a sort of syntactic sugaring:

public class PersonTest {

    /** Syntactic sugaring for having a hasName matcher method */
    public static Matcher<Person> hasName(final String name) {
        return new BaseMatcher<Person>() {
            public boolean matches(Object o) {
               return  ((Person) o).getName().equals(name);
            }

            public void describeTo(Description description) {
                description.appendText("Person should have the name ")
                           .appendValue(name);
            }
        };
    }

    @Test
    public void testPeople() {
        List<Person> people = 
            Arrays.asList(new Person("Steve"), new Person("Peter"));

        assertThat(people, hasItem(hasName("Peter")));
    }
}