This is all very "If a tree falls in a forest and no one is around to hear it, does it make a sound?" suggesting that reducing testing will reduce infections...
The data you need is what proportion of tests are positive. If, as suggested that more testing means more cases, then the positivity rate should remain constant. Unfortunately, the recent data does suggest that the proportion of PCR tests that are positive has gone way up since early November where it was around 9% to nearly 3% with the latest data shown in the first chart
here
Going forward however, we need to treat this with care as you only need a PCR test when symptomatic where before, you got one when you got a positive lateral flow result