def METHOD_NAME(self):
    # Virtual sites should be disabled by default
    self.assertIsInstance(
        self.system.virtual_sites,
        espressomd.virtual_sites.VirtualSitesOff)
    # Switch implementation
    self.system.virtual_sites = espressomd.virtual_sites.VirtualSitesInertialessTracers()
    self.assertIsInstance(
        self.system.virtual_sites, espressomd.virtual_sites.VirtualSitesInertialessTracers)