# unreliable.pl - Simulate a program that sometimes just hangs
if (rand(10) > 8){
  sleep 1 while 1 > 0;
}
else{
  print "--------------------------------\n",
        "It worked this time, no problems\n",
        "--------------------------------\n";
}
[download]

Expect.pm Test Program One
The following test program runs the unreliable program twenty times. If the unreliable program takes longer than five seconds, the attempt to run it is terminated and the test program continues.

# timeout.pl - Expect Test Program
use Expect;
my $timeout=5;
foreach my $i (1..20)
{
  my $exp = Expect->spawn("./unreliable.pl")
    or die "Cannot spawn unreliable process $!\n";
  $exp->expect($timeout);
}
[download]

Expect.pm Test Program Two
The next version of the test program adds the feature that a message is printed for the cases when a timeout occurs.

use Expect;
my $timeout=5;

foreach my $i (1..20)
{
  my $exp = Expect->spawn("./unreliable.pl")
    or die "Cannot spawn unreliable process $!\n";

  $exp->expect($timeout,
    [
      timeout =>
        sub
        {
          print "Process timed out.\n";
        }
    ]
  );
}
[download]

Expect.pm Test Program Three
The next version of the test program adds a check to see if the unreliable program prints "It worked" somewhere in its output. If the test program detects this string, it prints "Status: OK" after the unreliable program runs.

use Expect;

my $timeout=5;

foreach my $i (1..20)
{
  my $spawn_ok="not OK";

  my $exp = Expect->spawn("./unreliable.pl")
    or die "Cannot spawn unreliable process $!\n";

  $exp->expect($timeout,
    [
      'It worked',
        sub
        {
          $spawn_ok = "OK";
          exp_continue;
        }
    ],
    [
      timeout =>
        sub
        {
          print "Process timed out.\n";
        }
    ]
  );
  print "Status: $spawn_ok\n";
}
[download]