Nutrak 700 x 35-45C Schrader - self sealing inner tube

I ordered this inner tube, and received it on time, and fitted it to my bike. When I pumped it up I could hear a hissing noise. When I checked it I found that the valve was leaking. So the tube itself was fine, but useless because of the valve. How hard would it be for the manufacturer or retailer to check whether the tube works?

I didn't want to leave a review until I knew how effective the self-sealing was.I got a puncture last week (bit of glass went right through the tyre, leaving the tube no chance) and while I heard some air rush out, it quickly stopped. Not because the tyre was flat, but because the sealant had seemingly done its job. So I topped up the air and managed to get home.The puncture wasn't totally repaired, but I didn't expect it to be. I bought this tube to make sure I could get home without needing to repair a puncture miles from home and in that respect, it did its job.