IF these are exposed on an open floor where leakage from a test is not problematic, and IF this will always be run at low pressure and low flow, and IF your city pressure is high enough, then connect the two ends of the loop together with a ‘tee’ (use the standard fittings and connectors) and supply the ‘tee’ with city water for a few days. If it doesn’t leak at a high city pressure, it PROBABLY won’t leak at low pressure. If it does leak all over the floor, find the leak and repair it.
You sound like you are installing the PEX yourself without proper tools, fittings and connectors. That is not a good idea. If you are, call a qualified and licensed plumbing contractor to make up the floor fitting connections and pressure / leak test it.