SELECT T1.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"
What are the completion dates of all the tests that have result "Fail"?
SELECT T1.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 ''
select t1 . 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 = value
What are the completion dates of all the tests that have result `` Fail '' ?