You can cut down on the repetition a bit here by doing things like:

```
for test_gal in [ test_gal1, test_gal2, test_gal3]:
    # Test scale radius
    ...
```
rather than repeat the same test three times.

Also, the flux for these was 1, which you kept, but in general, we should avoid using exact 1's in unit tests, since it is easy for errors to be missed.  I like to use 1.7, but you can use anything.  (There are probably a ton of other places where this should be changed, but since I'm noticing it here, I'll mention it now.)