def tindex(spath=None):
spath = spath if spath else os.environ.get("<STR_LIT>", None)<EOL>if spath is None:<EOL><INDENT>return None<EOL><DEDENT>tests = []                          <EOL>for root, _, files in os.walk(spath):<EOL><INDENT>if root != spath:<EOL><INDENT>continue<EOL><DEDENT>tests += [f for f in files if f[-<NUM_LIT:3>:] in ["<STR_LIT>", "<STR_LIT>"]]<EOL><DEDENT>return tests<EOL>
Lists tindex in CIJ_TESTCASES

@Returns On success, a list of filenames is returned. On error, None is
returned