In one sentence, describe what the following article is about:

Before you purchase a violin, you should play the instrument. Most music shops will actually have a separate room for this purpose. Play the violin to get a sense of the feel and tone.  You should also have a friend or music teacher with you so that they can hear and test the instrument as well. Some shops will even allow you to take the violin home for a test period. Ask to see if that is possible and take advantage of the store’s policy. You may find that the violin sounds different once you get it home. Cracks in the wood can be expensive to repair and will impact the quality of the sound produced by the violin. Inspect the instrument for any cracks before purchasing. This is especially necessary if you are buying a used or antique violin. The ribs, or sides of the violin, should not bulge out beyond the edges of the top or back of the violin. This is typically a sign that the wood was not treated properly. It can also be common among violins that are over fifty years old. Consult a violin repair shop before purchasing a violin with this type of wear. The cost to make the repairs may be expensive. The bridge of the violin should be rounded, allowing for you to play a single string or multiple strings at the same time. If the bridge is flat at the top it may be very difficult to play a single note. The type and quality of wood can drastically impact the price of a violin. The best types of wood are spruce wood tops with maple wood necks, backs, and sides. Typically wood that has been aged for longer will be drier and stronger and is considered better quality for violins.  Ebony is typically used for the fingerboard. Less expensive violins may use cheaper wood types and may even have a plastic chin rest. If you are interested in buying an antique professionally made violin, such as a Stradivarious, you should make sure the instrument has been professionally appraised and authenticated before purchasing. There are only 600 Stradivari left in the world. An appraisal will help ensure that you avoid spending hundreds of thousands of dollars on a fake.

Summary:
Test the violin before purchasing. Look for cracks in the wood. Check the ribs for bulging. Check that the bridge is adequately curved. Ask what type of wood the violin is made from. Ensure an antique violin comes with an authentication certificate.