springboot-matcher.java

public static Matcher<List<Book>> containsTitle(final String title){
        return new BaseMatcher<List<Book>>() {
            @Override
            public boolean matches(Object item) {
                List<Book> books = (List<Book>) item;
                List<Book> booksFiltered = books.stream()
                        .filter(b -> b.getTitle().equalsIgnoreCase(title))
                        .collect(Collectors.toList());
                return !booksFiltered.isEmpty();
            }

            @Override
            public void describeTo(Description description) {
                description.appendText("The books list does not contain ").appendText(title);
            }
        };
    }