jsonpp: add test

Closes #26600.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
markdown: add test

Closes #26602.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
csvprintf: add test

Closes #26595.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
cowsay: add test

Closes #26593.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>