It’s important to test any iPhone/iPad app under low memory conditions to ensure that any objects in other view controllers or views that are required are still there after the warning. The simulators have a “Simulate Memory Warning” feature which is very helpful for debugging, but it’s still pretty far away from real-world usage to pause, mouse up to the menu, select the warning, and then see what happens. A low memory warning could have a different result if it arrives in the middle of an ongoing event (while something asynchronous is still going on, or during an animation for instance) instead of a few seconds later.
Which is why it can be helpful to make a keyboard shortcut for sending a warning. Go to the System Preferences>Keyboard>Application Shortcuts preference pane, click the “+” button, select application “Other” and then navigate to the iPhone Simulator under /Developer/Platforms/iPhoneSimulator.platform/Developer/Applications/, and then enter “Simulate Memory Warning” for the menu item and Command-1 for the shortcut. When testing in the simulator, interact with the mouse or trackpad with one hand and invoke memory warnings with the other at the same time. If you’re a lefty, Command-0 should work.