### Question:
LinkedMetadataManager { public Collection<String> getDatabases() { return providerMap.keySet(); } LinkedMetadataManager(Collection<MetadataProvider> providers); Collection<String> getTablespaceNames(); Optional<Pair<String, URI>> getTablespace(final String spaceName); Collection<Pair<String, URI>> getTablespaces(); boolean existsTablespace(String tablespaceName); Collection<String> getDatabases(); boolean existsDatabase(String dbName); Collection<String> getSchemas(@Nullable String dbName); Collection<String> getTableNames(String dbName,
                                          @Nullable final String schemaPattern,
                                          @Nullable final String tablePattern); void createTable(TableDesc desc); void dropTable(String databaseName, String schemaName, String tableName); boolean existsTable(String dbName, String schemaName, String tableName); TableDesc getTable(String dbName, String schemaName, String tbName);  }### Answer:
@Test public void testGetDatabases() throws Exception { assertEquals(Sets.newHashSet("space1", "space2", "default", "information_schema"), Sets.newHashSet(catalog.getAllDatabaseNames())); }