significant change to how run-tests works - is it OK?

Hi,

I just encountered one problem with run-tests - it uses backticks to
execute tests, like so:

$out = `$cmd`;

This is great for almost all situations.  Unfortunately, in very rare
cases, it is also necessary to test for return values.  For instance,
the shell-test command returns 1 or 0 - this is the only way to test its
output (by design).

Fortunately, by changing the code above to:

ob_start();
system($cmd, $return_value);
$out = ob_get_contents();
ob_end_clean();

it's possible to retrieve the return value and test based on it.
Otherwise, I will have to somehow run a test-within-a-test, which would
suck.

My question is: are there any situations that anyone knows of where
system() just doesn't measure up to the flexibility of shell_exec()?

Greg