PHOTOS as a pocket parton shower: flexibility tests for the algorithm

In this note we will recall the main tests that document robustness and flexibility of the PHOTOS design. This aspect may be of broader use and may find extensions in future applications, also outside the simple case of purely QED bremsstrahlung in decays. The components of the PHOTOS algorithm will be presented using operator language. The results of some flexibility tests, not documented before, will also be presented.