water softener conundrum: Not sure if my water softener is working or not

Hi,
I recently purchased a 12 year old home in Central Indiana that came with an water softener (waterboss model). The owners claimed it to be working during the closing. When we moved into the house, we filled the softener with salt and allowed the softener to regenerate. Then we tested the water from several faucets and sinks using a standard water softener test strip and it shows that the water is hard (between 180-250 ppm). However, at the same time the water feels quite slippery, esp. after washing with soap and the dishwasher absolutely leaves no scales.

Also I used the common test suggested in the web : taking a bottle, filling it halfway with water, adding dishwasher liquid and shaking to check for foam. That seems to wok pretty well too, the mixture foams up quickly and stays like that.

Should I replace my water softener ? Any other tests to check ? Just want to ensure that it is not working before buying a new one.

Any pointers will be greatly appreciated.

Thanks!