All burners check the photocell before ignition; that is they look for a 'no flame' situation. If the flame signal is there before ignition, the boxwill not open the solenoid valve, OR will run the burner in purge OR go to lockout, depending on the make.If you have a p/c that is not sensing, then after ignition, it will cut off the fuel.
To check for spark on site, it is satisfactory to disconnect the solenoid coil and start the burner outside the boiler, but be wary of allowing stray light into the p/cell. On Riello burners, this does not work as the control box checks the coil during the start up, but you can remove the coil from the valve, but you must place a 'keep' through the hole so that the coil does not implode.