def METHOD_NAME(self, input_data: "AtomicInput", config: "TaskConfig") -> "AtomicResult":
    self.ncalls += 1
    mode = self.iter_modes.pop(0)
    geom = input_data.molecule.geometry
    if geom.shape[0] != 2:
        raise ValueError("Failure Test must have an input size of two.")
    grad_value = np.abs(np.linalg.norm(geom[0] - geom[1]) - self.equilibrium_distance)
    grad = [0, 0, -grad_value, 0, 0, grad_value]
    if mode == "pass":
        return qcel.models.AtomicResult(
            **{
                **input_data.dict(),
                **{
                    "properties": {"return_energy": grad_value},
                    "return_result": grad,
                    "success": True,
                    "extras": {"ncalls": self.ncalls},
                    "provenance": {"creator": "failure_engine", "ncores": config.ncores},
                },
            }
        )
    elif mode == "random_error":
        raise qcng.exceptions.RandomError("Whoops!")
    elif mode == "input_error":
        raise qcng.exceptions.InputError("Whoops!")
    else:
        raise KeyError("Testing error, should not arrive here.")