I think soil testing is pointless, when adding that much organic matter.
The stuff releases on demand, from all the microbial and fungal action.
Those woodchip must contain every mineral that the garlic could ever need.
Forget the test kits and just observe which weeds pop up and other such indicators :)
I have to write that post...
I guess my rule of thumb is: If it's available in a shop, it's probably unnecessary.