Any puddles underneath? Has it been over heating? Remeber to check the coolant level (mid point on expansion tank) when the engine is cold and it will drop if warm/hot.
Could be any number of the plastic connectors or rubber hoses which can perrish like mine just did.
Do the pressure test but also check the cap as this can also leak.
My thermosat also gave up so you might want to do some preventative maintance on your car since it caused my radiator blow appart at the seams and break the inlet neck.
Happy hunting! Let us know what you find.