Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_31 (air_date VARCHAR, test_taker VARCHAR)
### Question:
On which air date was Robert the test-taker?
### Answer:
SELECT air_date FROM table_name_31 WHERE test_taker = "robert"