If we want to have a test case, we can add the following line to mne-scripts:
```
mne_do_inverse_operator --fwd sample_audvis-meg-eeg-oct-6-fwd.fif --depth --loose 0.2 --eeg --meg --diagnoise --inv sample_audvis-meg-eeg-oct-6-meg-eeg-diagnoise-inv.fif
```