Instead, could you change these to
```
with fits.open(...) as ...:
```

and then do the tests using each specific file within the with statement block.
The only reason I suggest doing it this way instead is that it will make sure all the files are closed before the test ends (whether or not it ends in failure).  This is not a problem on most platforms, but it *is* important on Windows where by default only one handle at a time can be opened for a given file :/

Otherwise these tests look fine, thanks.