How can I use the iOS Simulator to simulate an out of disk space condition?

Question

What is a practical way to test an "out of disk space" condition using the iOS Simulator?

Answer 1

Create a small disk image:

hdiutil create -size 2m -fs HFS+ /tmp/2meg.dmg 

Mount it to the relevant directory in your simulator app, e.g.:

hdiutil attach /tmp/2meg.dmg -mountpoint /Users/.../Library/Developer/CoreSimulator/Devices/.../data/Applications/.../Library/Caches 

Run app and perform your tests. This can also be done while the app is running. In this case you probably don't want to mount it as Caches or Documents directory directly because this would hide current files in those folders. Mount to a sub-directory instead. If this is not easily possible without changing paths in your app, mount the image somewhere else and copy data over before mounting it on top of the nonempty directory.

To unmount:

hdiutil detach /Users/.../Library/Developer/CoreSimulator/Devi... 

However, please note that the detach operation fails if the mount point is moved. This happens all the time because Apple renames simulator directories on iOS 8 every time an app is run. In this case use the mount command to find the device you have mounted, e.g. /dev/disk3s1 /Users/.../Library/..., then unmount the disk image using the device name instead of the mount point:

hdiutil detach disk3s1