The test runs ls -l /dev 2>/dev/null (which is different from find /dev/ -type c in that it isn't recursive); so check what its output is.

Or simply print out @c1 in the test, and look for which (presumably fake) entry ends with " 0" and starts with a "c".  (For example, in my case there is a line "total 0" — but as the latter starts with a "t", it doesn't interfere with the test...)

In other words, my guess would be this is something silly you need not really worry about, provided it's the only test that fails...