A test laboratory establishes the properties of something. How many bacteria are there in the meat? How much harmful radiation does a device emit? How many heavy metals are in the water? This is often established using measuring equipment. This equipment therefore has to be calibrated by a calibration laboratory. The test results are supplied to the client who then determines the meaning of the results. Is this brick hard enough for road use? Is this drinking water suitable for consumption? And so on. In principle, everything that can be measured is tested by a laboratory. The field of work of a test laboratory is therefore broad.