There are a number of ways to test pipes for leaks.
Sabricon recommends the Manometer test.
How To Test:
In this test you may fill the pipeline with water or you may use air. Air is much easier since you don’t have to transport the water to fill the pipeline. Seal off both ends and any connections to the pipeline using Drain Testing Plugs and connect the Manometer to one of the plugs. Fill the U portion of the manometer with water up to the red lines. Open the valve to connect the pump to the pipeline and using the handle provided begin to pump. Once the water has risen to the desired marking close the valve and time the dropping water level until it reaches balance again. The time it should take will be specified in your building codes for pipe testing.