This might sound like the start of a festive cracker joke, but is in fact the one of the main points of contention in the recent judgment, Claydon v Mzuri. The comparison was made in relation to an assessment of whether there had been a prior public disclosure during testing of a prototype agricultural seed drill. The prevailing case law, Mishan v Hozelock, relates to garden hoses.
For a patent to be valid, the claimed invention must be novel over the state of the art at the time of filing. The state of the art includes any public disclosure of the invention, whether written, oral, or based on a prior use. Further, it is not even necessary that a member of the public actually reads, hears or sees the disclosure.
No public disclosure was found to have taken place in Mishan v Hozelock because the inventor gave evidence to the effect that he would have hidden the prototype garden hose from anyone passing his garden while testing took place. However, although the inventor made similar comments in Claydon v Mzuri the judge in this latter case held that it was not possible effectively to hide a seed drill attached to a tractor from a hypothetical skilled-passer-by peering through a real hedge, at the edge of a real field.
This case is quite fact specific, but does demonstrate the limitations of a rebuttal based on Mishan v Hozelock to an alleged prior public disclosure.
If you intend to test a new invention somewhere public, you might wish seek advice from a patent attorney beforehand.