public PackageRepository find(final String repoId) {
        return stream().filter(repository -> repository.getId().equals(repoId)).findFirst().orElse(null);
    }
@Test
    void shouldReturnNullIfNoMatchingRepoFound() throws Exception {
        PackageRepositories packageRepositories = new PackageRepositories();
        assertThat(packageRepositories.find("not-found")).isNull();
    }