Whenever a leak detection system is installed on a pipeline there is the need to test the functionality. This can be either to ensure the performance of the leak detection system or to meet official requirements and regulations. For leak detection system vendors this is a recurring task, but operators often encounter the question which tests have to be performed and how for the first time. The paper describes several test methods that are applied in practical applications. The test methods will be explained and their respective benefits will be shown. Furthermore it will be described which factors influence the choice and the set-up of the tests. These include for example the method or combination of leak detection systems as well as the real layout and the conditions of the pipeline system. To complete the overview practical examples and a typical test procedure will be shown.