testing: shutdown hook?

[bradfitz]

Could we add a shutdown/cleanup mechanism to the testing package?

Background: some tests (notably: integration-style tests) require heavy setup, compiling
things, setting up things on disk, running child processes wired together, etc.

If you just do this once and share it per test, it's unclear when to clean up the /tmp
folder and shut down the processes.

People have resorted to things like TestZZZ for cleanup (which doesn't work well with
-test.run), or z_last_test.go (as seen in net/http), or the hoops jumped through here:

https://github.com/bradfitz/docker/blob/fuse/vfuse/all_test.go

(Look at release and testsToRun and how it's calculated.)

And also hacks in Google's code, even people so far as to fork the testing package.

Or people run a child process that is responsible for cleanup, once it notices its
parent has died. But that's a lot of work and there are portability concerns.

I know a test could still crash mid-way through, so cleanup on shutdown is still best
effort, but when it's a bunch of big processes and big files in /tmp, that's better than
nothing most the time.

With regard to atexit-ish concerns, I'd propose the shutdown mechanism itself be subject
to the same timeout concerns.  If the shutdown doesn't finish in N seconds, the test
exits with failure.

[chai2010]

Comment 1:

I think we need a testing.Atexit to do the clean work.
CL13729043 has some discuss about the testing.Atexit.
https://golang.org/cl/13729043/

[rsc]

Comment 2:

I don't see Atexit happening. It's too awful.
issue #8202 describes an alternative.

[balshetzer]

Comment 3:

We could add some more conventions:
If a function called SetUp exists then it runs before any of the tests.
If a function called TearDown exists then it runs after all the tests have run.
More generally, we could have:
If a function starts with SetUp(.*) and takes *testing.T then it will be run before any
of the tests that start with Test\1 are run.
If a function starts with TearDown(.*) and takes a *testing.T then it will be run after
all of the tests that start with Test\1 are run.
This can lead me to write something like:
func SetupCaseFoo(t...
func TestCaseFooBar(t...
func TestCaseFooBlee(t..
func TearDownCase(t..
etc.
If the concern is that there might already be functions with such names and argument
types then a new type could be introduced that must be the argument that is an alias for
testing.T (or that is more specifically suitable for setup and teardown functions).

[rsc]

Comment 4:

Status changed to Duplicate.

Merged into issue #8202.