The only way to test it is to send it to a testing lab unless you want to spend a whole lot of money on equipment. Even that would cost more than a new cable.
The best way to verify compliance is to get your supplier to send you a copy of his compliance certificate. If he has a pre-1.3 certificate for a length at least as long as your cable, the cable is 1.4 compliant as a "standard" HDMI cable. If he has a 1.3 certificate or 1.4 certificate indicating "Category 2" or "High Speed," then it's 1.4 compliant as a "high-speed" cable.