Review Regression Tests

Review each regression test set and make any necessary revisions or additions.

Regression tests can be run by using the command 'make installcheck' in the incubator-age directory on your local machine.

The regression tests can be found in the /regress/sql folder. When regression tests are run, result files will be generated in /regress/results and diffed against /regress/expected. A diff file while be generated to show any differences between the expected vs actual result. Please be sure to reference these files when updating regression tests. The regression tests pass if and only if when result == expected.

It is important to check for possible uncovered test cases, and write more robust tests when necessary.