java - 断言 Set 包含具有返回给定值的方法的对象

Question

类 A 有一个方法 getId()，它返回一个字符串。

B 类有一个方法 getCollection()，它返回一个 Collection(顺序未定义)

我希望我的测试能够验证返回的集合是否包含 A 的实例，每个实例都返回 getId() 的预期值

public interface A {
    String getId ();
}

public interface B {
    Collection<A> getCollection ();
}

public class BTest {

    @Test
    public void test () {
        B b = ( ... )
        Collection<A> collection = b.getCollection();
        assertEquals(3, collection.size());

        String expId1 = "id1";
        String expId2 = "id2";
        String expId3 = "id3";

        // There should be 3 A's in this collection, each returning
        // one of the expected values in their getId()
    }

}

我只能想到一些非常不优雅的东西。我目前正在使用 JUnit/Hamcrest/Mockito。如果最好的解决方案意味着库，那不是问题

Answer 1

Java-8解决方案，够优雅吗？

public class BTest {

    @Test
    public void test () {
        B b = ( ... )
        Set<String> expectIds = new HashSet<>(Arrays.asList("id1","id2","id3"));
        Collection<A> collection = b.getCollection();
        Set<String> ids = collection.stream().map(a->a.getId()).collect(Collectors.toSet());

        assertEquals(3, collection.size());
        assertEquals(expectIds, ids);

    }

}

编辑:

断言J:http://joel-costigliola.github.io/assertj/assertj-core-features-highlight.html

public class BTest {

    @Test
    public void test () {
        B b = ( ... )
        Collection<A> collection = b.getCollection();

        assertEquals(3, collection.size());
        assertThat(collection).extracting("id").contains("id1","id2","id3");
    }
}