I have UI tests which testing login functionality (and uses it to test other stuff), but sometimes when focus is changed from one field to another - the keyboard hides, and
Following Brooks great answer, this will work for all simulators:
/usr/libexec/PlistBuddy -c "Print :DevicePreferences" ~/Library/Preferences/com.apple.iphonesimulator.plist | perl -lne 'print $1 if /^ (\S*) =/' | while read -r a; do /usr/libexec/PlistBuddy -c "Set :DevicePreferences:$a:ConnectHardwareKeyboard
false" ~/Library/Preferences/com.apple.iphonesimulator.plist || /usr/libexec/PlistBuddy -c "Add :DevicePreferences:$a:ConnectHardwareKeyboard
bool false" ~/Library/Preferences/com.apple.iphonesimulator.plist; done