All these tests already explicitly test against both legacy PM and NPM.
$ sed -i 's/ -attributor / -attributor -enable-new-pm=0 /g' $(rg --path-separator -l -- -passes=)
$ sed -i 's/ -attributor-cgscc / -attributor-cgscc -enable-new-pm=0 /g' $(rg --path-separator -l -- -passes=)
Now all tests in Transforms/Attributor/ pass under NPM.