How to test for block change

Solution 1:

/testfor is for entities only. If you want to check a block instead, use /testforblock.

It looks like you've copied the coordinates from your exact feet position. These may not end up rounding correctly to a block position; I'd recommend using the Looking At values instead:

The following command will test for a heavy weighted pressure plate at (-88,65,-68), regardless of its power level:

/testforblock -88 65 -68 heavy_weighted_pressure_plate

You can then test for a specific power level with blockstates like this:

/testforblock -88 65 -68 heavy_weighted_pressure_plate power=1