LDR light dependant resistor, potmeter is a variable resistance... if you swap the LDR by a potmeter you can test the system without actually having to use light...
By getting the curve of the resistance/light of the LDR, you can then simulate with the potmeter any point of light based on the resistance. Thus testing the accuracy of your light measurement and control of the system.
By the way, all those floats... they could be moved into memory. 