Assuming you have a modern meter with an LCD display and a flashing LED which shows how much power you are using (1 flash = 1 watt hour) then you can do a crude test as follows.
Turn everything off at the tableau except one lighting circuit and on that circuit make sure a single 100W bulb is turned on. Now look at the meter - if the LED flashes once every 36 seconds the meter is OK. It's a crude test as the power the bulb takes will depend on manufacturing variations and also on the voltage present at your property. A 60W bulb will make the LED flash once a minute.
A more accurate way of doing it is to get one of these https://www.amazon.fr/consommation-d%C3%A9nergie-m%C3%A8tre-wattm%C3%A8tre-compteur/dp/B00E5BONDU/ref=sr_1_5?ie=UTF8&qid=1487280612&sr=8-5&keywords=metre+puissance (or similar, this is just the 1st I found on Amazon, not a specific product recommendation) and compare the reading on it with the main electricity meter - again you would have to make sure everything is turned off except one load plugged into the power meter. you can then check your LED is flashing at the right rate (60W - once per minute, 120W once every 30secs, 180W once every 20 secs and so on - the load in watts is how many times the LED should flash per hour).
As to 900€ for a year that does seem high - if you are on a 12kW supply on tariff bleu then that is almost 5000kWh a year, even a large 'fridge should be less than 1/10 that amount. It is roughly equivalent to a continuous load of 500W.
Are you sure that you are turning everything off?
Have you taken readings at the beginning and end of your stay and worked out how much you have used while there? Readings when you are away would be useful as well. Have you looked in detail at the bill?