Summarize this article:

The doctor will likely order these tests first to make sure you don't have a stomach blockage. A stomach blockage can cause symptoms that are similar to gastroparesis.  For an endoscopy, your doctor will use a tiny camera on a flexible tube. You'll first be given a sedative and likely a throat-numbing spray. The tube will be threaded down the back of your throat and into your esophagus and upper digestive tract. The camera will help your doctor see what's going on more directly than they can with an X-ray.  You may also receive a similar test called an esophageal manometry test to measure stomach contractions. In this case, the tube will be inserted through your nose and left in for 15 minutes. If the doctor doesn't see a blockage in the other tests, they'll likely order this study. This test is a bit more interesting. You'll eat something (such as a an egg sandwich) that has a low dose of radiation. Then the doctor will look at how long it takes you to digest it by using an imaging machine. Typically, you'll get a diagnosis of gastroparesis if half the food is still in your stomach after an hour to an hour and a half. An ultrasound will help the doctor detect if some other issue is causing your symptoms. Particularly, they will look at how well your kidneys and gallbladder are functioning with this test. If the doctor is having a hard time explaining your symptoms, you'll likely have this test done. Basically, it's a way of listening to your stomach for an hour. They'll put electrodes on the outside of your belly. You must have an empty stomach for this test.

Summary:
Be ready for an endoscopy or X-rays. Expect a gastric emptying study. Ask about an ultrasound. Be ready for an electrogastrogram.