def METHOD_NAME(self):
    """Verify that the current position can be read and not written."""
    pos = self.focus_tracker.position.value["z"]
    self.assertIsInstance(pos, float)
    self.assertGreaterEqual(pos, -10e-6)  # In theory, it can be a tiny bit negative, but it's unlikely
    # It should be in m. The distance is typically < 1mm. So let's say always < 10cm
    self.assertLess(pos, 0.1)
    with self.assertRaises(NotSettableError):
        self.focus_tracker.position.value = {"z": 10}
    # After a while the position should change (at least, just due to noise):
    positions = [pos]
    for i in range(10):
        time.sleep(0.1)
        positions.append(self.focus_tracker.position.value["z"])
    # At least 2 positions different
    self.assertGreaterEqual(len(set(positions)), 2, "All positions reported are %s" % (pos,))