def METHOD_NAME(self, ad_ag1, ad_ag3, ad_ag4):
    '''Test exceptions raised when number of atoms do not
    match or AtomGroups come from different trajectories.'''
    # number of atoms do not match
    match_exp_atoms = "AtomGroups do not"
    with pytest.raises(ValueError, match=match_exp_atoms):
        ad_atoms = ad.AtomicDistances(ad_ag1, ad_ag3)
    # AtomGroups come from different trajectories
    match_exp_traj = "AtomGroups are not"
    with pytest.raises(ValueError, match=match_exp_traj):
        ad_traj = ad.AtomicDistances(ad_ag1, ad_ag4)