If I was testing anything else, set_eval_limit would have been the way to go.  The call_out tests are a bit troublesome, though.  For any other case, I could have done something like:
<pre>
1) Call max_eval_cost() and save the old limit
2) Use set_eval_limit() to change the limit as needed for the test
3) Run the test
4) Use set_eval_limit() again to restore the old, saved limit
</pre>

But because we're testing call_out, the do_tests() function returns before the tests complete (because they're scheduled to run later through call_out.)  So any changes made to the eval limit will affect tests which run afterward, because there is no opportunity to change it back synchronously.

So, considering that whatever I do, there will be side-effects on other tests, I felt it was best to change the setting in the most conspicuous place possible (the driver config), rather than bury it in single/tests/efuns/call_out.c.  If an unrelated test fails intermittently because of eval_cost, the cause of the failures will be easier to find and fix (by raising the limit slightly.)