Different ways. There are several different tests we can do to help ascertain a crack in the tooth.
Various test. A dentist can visually see a crack or take an x-ray to verify a crack..
X-ray & test. Your dentist can x-ray and test for a cracked tooth. Depending on how far the crack goes, a cracked tooth can sometimes be repaired.
Thorough diganosis. Some cracks are large and easily diagnosed, however the majority are small ones that are undetectable on xray. Patients with cracked teeth complain of pain when biting. Some can only be diagnosed by eliminating other causes. In most cases, you can diagnose a partial crack in a tooth by having you bite on instruments that put pressure on different parts of the tooth to elicit pain.