Add an empty file to the location where the service file will be
created in the b.json version of the test. This way, we will get a
content hash of the created file which is a slightly better test than
just knowing that it was created.
Note that, in the diff, the "before" checksum is the empty file hash:
echo -n '' | sha256sum
e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 -