instruction: A bar chart for returning the number of the completion date for all the tests that have 'Fail' result, and rank from low to high by the the number of date of completion.
response: SELECT date_of_completion, COUNT(date_of_completion) FROM Student_Course_Enrolment AS T1 JOIN Student_Tests_Taken AS T2 ON T1.registration_id = T2.registration_id WHERE T2.test_result = "Fail" GROUP BY date_of_completion ORDER BY COUNT(date_of_completion)