Fully green rows ("works as expected") are not shown.
The timeout for each test is 5 seconds. On my machine increasing the timeout to 8 seconds allows all tests to finish.
Busybox awk does not support the NUL character U+0000.
"Result undefined" refers to the JSON specification. So "result undefined, parsing succeeded" (failed) means that in the absence of a clear expectation, the implementation succeeded or failed at parsing the input JSON text.