A link to a sample disclosure request document is located on the OP. The sample disclosure request shows a request for the officers notes. The officer would need to note such testing done as per the radar gun's manufacturer's instructions. At some point you "could" visit the prosecutor's office and ask to view the radar's manual (if you are unable to find a copy of it online). With that you can make copies. Then at trial, you can question the officer if he did test the gun, and on how he tested it (to verify if he did it as per the manual).
If you can show that the officer did not perform testing as per the manufacturer's instructions. Then you have shown reasonable doubt that the radar gun was working. Showing that the radar gun was functioning is evidence that that the prosecutor needs to prove you were speeding, which means you cannot be convicted of that offence if the police officer didn't perform the testing as per the manual.