@Test
public void populatesPostsToLikes() {

    String id = "someId";
    Like like = mock(Like.class);
    List<Like> likes = Arrays.asList(like);
    Map<String, Post> postMap = new HashMap<>();
    Post post = mock(Post.class);
    postMap.put(id, post);
    when(like.getPostId()).thenReturn(id);
    LikesFeed feed = new LikesFeed();
    feed.likes = likes;
    feed.users = new HashMap<>();
    feed.posts = postMap;
    feed.flatten();
    verify(like).setPost(post);
}