### Question:
GraphStoreCatalog { public static Optional<Graph> getUnion(String username, NamedDatabaseId databaseId, String graphName) { return getUserCatalog(username).getUnion(UserCatalog.UserCatalogKey.of(databaseId, graphName)); } private  GraphStoreCatalog(); static GraphStoreWithConfig get(String username, NamedDatabaseId databaseId, String graphName); static void set(GraphCreateConfig config, GraphStore graphStore); static Optional<Graph> getUnion(String username, NamedDatabaseId databaseId, String graphName); static boolean exists(String username, NamedDatabaseId databaseId, String graphName); static void remove(
        String username,
        NamedDatabaseId databaseId,
        String graphName,
        Consumer<GraphStoreWithConfig> removedGraphConsumer,
        boolean failOnMissing
    ); static int graphStoresCount(); static int graphStoresCount(NamedDatabaseId databaseId); static Optional<Map<String, Object>> getDegreeDistribution(String username, NamedDatabaseId databaseId, String graphName); static void setDegreeDistribution(String username, NamedDatabaseId databaseId, String graphName, Map<String, Object> degreeDistribution); static void removeAllLoadedGraphs(); static Map<GraphCreateConfig, GraphStore> getGraphStores(String username); static Map<GraphCreateConfig, GraphStore> getGraphStores(String username, NamedDatabaseId databaseId);  }### Answer:
@Test void getUnion() { GraphStoreCatalog.set(CONFIG, graphStore); var actual = GraphStoreCatalog.getUnion(USER_NAME, DATABASE_ID, GRAPH_NAME).get(); TestSupport.assertGraphEquals(graphStore.getUnion(), actual); }