An unprovable testsuite for cat

create_cat_testdata.sh

#!/bin/bash
i=0
while true
do
        pass=`cat /dev/urandom | tr -dc A-Za-z0-9 | head -c $i`
        echo $pass > ./testcases/length_$i.txt
        i=$(($i + 1))
        sleep 1
done

run_cat_tests.py

from subprocess import check_output, CalledProcessError

length = 0
passes = 0
while True:
    try:
        output = check_output(['cat', './testcases/length_%s.txt' % length])
    except CalledProcessError:
        print
        print 'Test suite complete'
        print '%s passes out of %s execution' % (passes, length)
        break
    
    testfile = open('./testcases/length_%s.txt' % length)
    testdata = testfile.read()
    if output == testdata:
        print ".",
        passes += 1
    else:
        print "F",
    
    length += 1

You're wasting a ton of entropy, man! There's a limited amount of that stuff.

pass=`cat /dev/urandom | base64 | head -c $i`