FUSE integration doesn't have automated tests

[zooko]

We just discovered that the FUSE extension that nejucomo had contributed had bit-rotted. This is what happens to software that doesn't have automated tests.

Nejucomo and I have chatted about it, and he says it is hard to make isolated tests for the Python FUSE library because the only way to use it is to subclass it, and you cannot instantiate your subclass without hooking into a running Linux kernel. :-)

[warner]

Yeah, that will be fun :-). The way to do it is to run the buildslave on dedicated machine (perhaps a VM) that has a couple of setuid scripts that can run the mount/umount commands (maybe speak foolscap to a server running as root that will run those commands upon request). The builder then needs to do:

• upload tahoe tree, build
• restart a local tahoe node, connecting to an existing grid
  • (see the speedtest buildslave for details, it does the same thing)
• sudo mount the FUSE filesystem, using that local node as the backend
• list /mnt/tahoe, modify files there, make sure it works
  • use GET?t=json on the node to make sure the changes are actually reflected in the backing store
• sudo umount the FUSE filesystem

Of course, if we want to assert that the FUSE plugin will work against other Tahoe versions (not just HEAD), then it could use an existing tahoe node (running a known version) instead of updating and restarting a node each time. This probably won't be appropriate until Tahoe's HTTP API has stabilized a bit.

[zooko]

arch_o_median is working on a test script which exercises the FUSE extension. archie: the test script is not require for v0.7.0, although #36 -- "FUSE integration" -- would be really good to have in v0.7.0. The test script might be a good way to guide yourself to finishing #36.

[zooko]

nejucomo has added some tests -- see ​the revision control log of the {{{contrib/fuse}}} directory.

nejucomo: would you please close this ticket and open a new one describing more specific tests that you want to add?

[nejucomo]

There are tests in the "runtests.py" script accompanying tahoe_fuse.py (fuse_a).

There is one trivial unit test that this script executes. Then it executes what I call "system tests" because they are not certainly deterministic, and involve launching processes, various race conditions, and other ugliness.

All this being said, they seem to work on my system. (They have bitrotted since introduced, and I'm close to submitting a patch which updates them for allmydata 1.0.0-r2528 and ubuntu python-fuse 1:0.2-pre3-3.)