Yes, a plumbing test after foundation repair is usually worth doing, and a test before the repair is just as useful. Lifting or leveling a slab can crack or pull apart the drain and water lines under it, and that leak can stay hidden under the floor. Testing on both sides of the repair shows what the work changed.
Two different tests cover the two systems. A hydrostatic test checks the drains: the main building drain is plugged, usually at the cleanout, the pipes under the house are filled with water up to slab level, and the plumber watches whether the level drops. A static pressure test checks the supply side: a gauge goes on a hose bib, the water is shut off at the meter, and the gauge shows whether pressure falls. Some cities put this in the permit. The Farmers Branch post foundation repair test form calls for a 15 minute water pressure test and a 30 minute drain test before final inspection.
The test before the repair matters because the same clay soil movement that cracked the foundation is also one of the common causes of slab leaks. Without a baseline, nobody can say whether a later leak came from the lift or was already there. Read your foundation contract or warranty for any test it calls for, and keep the results.
One honest limit: a passed test is a snapshot. It shows the pipes held on that day, and clay keeps moving with the seasons. A failed hydrostatic test also says a drain leaks somewhere under the slab, not where. A camera inspection of the drain line, or plugging sections one at a time and retesting, narrows it down. Later on, the signs of a slab leak you can check yourself are worth knowing.