Of course, refurbished iPhones are fully tested. In fact, when an iPhone is getting refurbished, testing is one of the most important stages. The testing process includes:  hardware tests; software tests; thorough checking of all components. Because a refurbished iPhone is generally in great working condition, most parts will pass the checks without a problem. However, if any part seems defective, it will go through troubleshooting. Whenever possible, the refurbisher will fix the faulty part. If it cannot be fixed, the refurbisher will replace the part with a brand new one. For instance, a cracked screen is systematically replaced with a brand new screen. Once any necessary fixes or replacements are done, a refurbished iPhone goes through the product testing process once more. This is important to understand: refurbished iPhones go through the same testing process as any new iPhone does. You can expect the same level of functional quality from a refurbished iPhone as you do from a brand new device.