/testforblocks are all part of the same group of commands and are similar in what they do after their test. They are only useful when their output is measured using redstone comparators (not recommended) or when combined in a chain with other commands (most often way)
It's quite simple. If the test returns TRUE, any conditional command blocks later in the chain will run (unless stopped by a different failed command in between). If the test returns FALSE, the conditional command blocks won't run.
I would like to invert the check, so that if the entity does not exist
/testfor, or if the block is not what is specified
/testforblock, or if the block regions don't match
/testforblocks, then the subsequent commands in the chain will run, and if the check passes, they will not run. How can I do this?
(I suspect that for
/testforblock, it's as simple as placing a
! before the block name, but I'm not sure if the
! operator existed in 1.12. For
/testforblocks, absolutely no idea.)
Please also consider viewing my other, identical question for Minecraft Bedrock Edition.