There might be no way of predicting why you might come to the attention of the police but I don’t think there’s a single case of people being prosecuted with the greyer areas of airgun law without something else bringing them to the attention of the police beforehand. Generally the police have better things to do without feeling the need to knock on doors and get rulers and chronos out, and their need to test your gear will need to be related to their concerns. They need justification for seizure and testing. In other words you already need to be under suspicion of something to be worried.