Describe the bug
There are several different test case syntaxes which do not follow single logick.

Current behavior
As for now you can look into jq.test and find syntaxes:

1. Header describing file syntax - program + input + output. But this is totally wrong!
2. %%FAIL - assert error with specified message (no program/output are provided).
3. %%FAIL IGNORE MSG - assert error with any message.
4. # Runtime error - comment that must be ignored but actually asserts fail.
5. No output at all - actually this must be [] but somehow just no line generates successful pass for test.
6. Multiline output - this is only one logical hack, but still is hack.
7. BOM at line start - well, whole file is already parsed to memory so wtf?
8. JSON unparsable values - mostly type overflow and incorrect values (likely from JSON5). This is very strange for json tool to have unsupported json values...
9. {x: -1}→null→{"x": -1} - just wrong output. Can you see one extra space? This is false positive test.

Expected behavior
Each test case must be normalized to well-documented format. To my mind it should be JSON format with schema. Example:

true
null
true

should be converted to

{
  "filter": "true",
  "inputs": [null],
  "outputs": [true]
}

Notice that this is JSON but raw cli string.