public Set<ContentPackInstallation> findByContentPackIdAndRevision(ModelId id, int revision) {
        final DBQuery.Query query = DBQuery
                .is(ContentPackInstallation.FIELD_CONTENT_PACK_ID, id)
                .is(ContentPackInstallation.FIELD_CONTENT_PACK_REVISION, revision);
        try (final DBCursor<ContentPackInstallation> installations = dbCollection.find(query)) {
            return ImmutableSet.copyOf((Iterator<ContentPackInstallation>) installations);
        }
    }
@Test
    @MongoDBFixtures("ContentPackInstallationPersistenceServiceTest.json")
    public void findByContentPackIdAndRevisionWithInvalidId() {
        final Set<ContentPackInstallation> contentPack = persistenceService.findByContentPackIdAndRevision(ModelId.of("4e3d7025-881e-6870-da03-cafebabe0001"), 3);

        assertThat(contentPack).isEmpty();
    }