def METHOD_NAME(self):
    # Add overlay above the source node so that we actually use a
    # commit job instead of a mirror job
    iotests.qemu_img('create', '-f', iotests.imgfmt, self.overlay_img,
                     '1G')
    result = self.vm.qmp('blockdev-add', **{
        'node-name': 'overlay',
        'driver': iotests.imgfmt,
        'file': {
            'driver': 'file',
            'filename': self.overlay_img
        }
    })
    self.assert_qmp(result, 'return', {})
    result = self.vm.qmp('blockdev-snapshot',
                         node='source', overlay='overlay')
    self.assert_qmp(result, 'return', {})
    self.do_test_stop('block-commit', device='drive0', top_node='source')