In IIS 7 and 7.5
Go to Advanced settings for the app pool
In Rapid Fail Protection,Enable = true, set Maximum Failures=1
Right click on application pool->Properties
Click on Health tab
Enable Rapid fail protection should be checked and change Failures to 1
What this will help you is to catch application pool crash easliy. The default value for failures is 5.Which means for the first 5 crashes the application pool will recover itself.So if your goal of testing is to detect crash on load, you might need 5 times load to replicate the issue.