The correct answer is: All of these.
A water test is a common method for testing sewer pipes. It involves filling the pipe with water and then checking for leaks. A ball test is another method that can be used to test sewer pipes. It involves dropping a ball into the pipe and then checking to see how long it takes to reach the bottom. A mirror test is a less common method that can be used to test sewer pipes. It involves inserting a mirror into the pipe and then checking to see if there are any cracks or other damage.
Water tests are the most common type of sewer pipe test. They are relatively easy to perform and can be used to detect a variety of problems, including leaks, cracks, and blockages. Ball tests are less common than water tests, but they can be more effective at detecting small leaks. Mirror tests are the least common type of sewer pipe test, but they can be the most effective at detecting small cracks and other damage.
All three of these tests can be used to test sewer pipes. The best test to use will depend on the specific situation. For example, if you are concerned about a leak, a water test may be the best option. If you are concerned about small cracks or other damage, a mirror test may be the best option.