Some basic tests can be done at your GP surgery.
One of these is called a peak flow test You will be asked to take a full deep breath in, close your lips around the mouthpiece to form a seal and then blow as hard and fast as you can into mouth piece. Usually three readings are done to get an accurate score. You might be asked to take a peak flow meter home and keep a diary for a few days to check if there are certain times of the day when you get most symptoms. You can find out more about this in the Peak flow section on this website.
You may also have a test called spirometry. This test is more accurate as it measures how your lungs are working and the results are compared to what would be expected from someone of your age, size and ethnic group. You can find out more about this in the Spirometry section on this website.