Can someone still get a positive pregnancy test after a tubal liguation. How long after can they test to have a positive test.

Tubals can fail. Just like after a vasectomy, failure rates are less than 1% but still can occur at any time. A pregnancy test will turn positive about two weeks after actual conception.
Tubal ligation. Even a tubal ligation is not 100% effective for protection against pregnancy. (although the failure rate is very low). Please let your gynecologist/ obstetrician know asap if you are pregnant as there is an increased risk for ectopic/ tubal pregnancy. Take care.