Are there any preoperative tests for a colonoscopy?

No, not necessarily: Certainly doctors might want to do testing if there are medical conditions that might cause instability during mild anesthesia or demonstration of tranquilizers, or if there is some clotting disorder, cirrhosis. Absent those types of circumstances, no testing is routinely warranted.

Not Typically: Routine colonoscopy, facilitated by intravenous sedation to minimize discomfort, does not require preop testing in healthy individuals. However, for people with chronic medical issues, who are advancing in age, taking prescribed medications or are dealing with acute medical problems any number of lab tests may be ordered to assure your safety; cbc, chemistries, liver function tests, etc.