Please see this
MDA Report for Medela phototherapy - they outlin the test and equipment they used on this very device...
As well as the peak blue light output measurement, you should also measure the area in which the output is > 1mW/cm2 - this should be measured at a height of 40 cm above the measuring device.
For preterm babies this area must be > 300 cm2 and term babies > 700cm2.