For testing climate you need a climate tester (climate chamber). Such equipment can be large and sophisticated (se photo) or simple. The climate chamber on the photo can both control temperature and humidity in cyclic test procedures controlled by a computer. Temperature range is from -400C to 600C.
More simple equipment can also be used. Standard refrigerators or freezers can be used if you only need temperature control in your tests. Humidity can also to some degree be controlled by either adding water or using water absorbing materials.