So there a couple of things that are wrong. The first is that I put a comma on the line, because I thought the config file was Ruby and Shell. My bad, perhaps documentation bad? Since comments are prefixed with hashes anyway, include the shebang on line 1 of the example file so we all know what type of file we're dealing with.

The error is because whatever is processing the config file is firing up an interactive shell, somehow.

$ cat mine
sample: test.check "true", "true"
$

{"result": false, "changing": true}

stty: stdin isn't a terminal