How I can test the power supply across the load?
how can i test this power supply?

Start by using the right load.  The supply is rated for 10 A maximum at 12 V.  By Ohm's law, that means the smallest valid load resistance is (12 V)/(10 A) = 1.2 &Omega;.

By connecting a 700 m&Omega; resistor to the supply, you violated it's current spec.  Again by Ohm's law, (12 V)/(700 m&Omega;) = 17 A.  The supply dropping its output voltage when you attempt to draw more than rated current from it is a totally reasonable thing for it to do.

You really need to look up Ohms's Law and understand what it means.

Also consider the power the load resistor must dissipate.  If you manage to load the supply to its maximum rating, then the power into the resistor will be (12 V)(10 A) = 120 W.  Even if your resistor were the right resistance, it doesn't have enough power handling capability.

You could get a second 700 m&Omega; 100 W resistor and put them in series.  That effectively makes a 1.4 &Omega; 200 W resistor.  That is within what the supply can drive and the combined resistance can handle.  By Ohm's law again (yes this comes up a lot and is really useful), (12 V)/(1.4 &Omega;) = 8.6 A.  That's what the current will be thru the combined resistor.  It doesn't test the supply to the limit, but it's a good start.