def METHOD_NAME():
    """Test for narrowband fitter class F-test."""
    m = tm.get_model(os.path.join(datadir, "J0023+0923_ell1_simple.par"))
    t = simulation.make_fake_toas_uniform(
        56000.0, 56001.0, 10, m, freq=1400.0 * u.MHz, obs="AO"
    )
    f = fitter.WLSFitter(toas=t, model=m)
    f.fit_toas()
    # Test adding parameters
    F2 = param.prefixParameter(
        parameter_type="float",
        name="F2",
        value=0.0,
        units=u.Hz / u.s / u.s,
        frozen=False,
    )
    ft = f.ftest(F2, "Spindown", remove=False)
    assert isinstance(ft["ft"], (float, bool))
    # Test return the full output
    Ftest_dict = f.ftest(F2, "Spindown", remove=False, full_output=True)
    assert isinstance(Ftest_dict["ft"], (float, bool))
    # Test removing parameter
    F1 = param.prefixParameter(
        parameter_type="float", name="F1", value=0.0, units=u.Hz / u.s, frozen=False
    )
    ft = f.ftest(F1, "Spindown", remove=True)
    assert isinstance(ft["ft"], (float, bool))
    Ftest_dict = f.ftest(F1, "Spindown", remove=True, full_output=True)
    assert isinstance(Ftest_dict["ft"], (float, bool))