Amends 76c63936d3 by adjusting the test case.
We still just test that we can open a file based on a filename that we came
up with ourselves.
Also, update usage documentation and make the snippet a bit more relevant.
Change-Id: I5bf00210d74e2a73d5a71a09a5beb1b3f6f8e225
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>