[lldb-dev] lldb tests and tear down hooks

Pavel Labath via lldb-dev lldb-dev at lists.llvm.org
Wed Oct 21 02:07:17 PDT 2015

I think we can remove these, provided there is a way to mimic the
functionality they are used for now, which I think shouldn't be hard.
Anything which was set up in the setUp() method should be undone in
tearDown(). Anything which was set up in the test method, can be
undone using a try-finally block. Is there a use case not covered by


On 21 October 2015 at 04:47, Zachary Turner via lldb-dev
<lldb-dev at lists.llvm.org> wrote:
> There's a subtle bug that is pervasive throughout the test suite.  Consider
> the following seemingly innocent test class.
> class MyTest(TestBase);
>     def setUp():
>         TestBase.setUp()    #1
>         # Do some stuff      #2
>         self.addTearDownHook(lambda: self.foo())   #3
>     def test_interesting_stuff():
>         pass
> Here's the problem.  As a general principle, cleanup needs to happen in
> reverse order from initialization.  That's why, if we had a tearDown()
> method, it would probably look something like this:
>     def tearDown():
>         # Clean up some stuff  #2
>         TestBase.tearDown()    #1
> This follows the pattern in other languages like C++, for example, where
> construction goes from base -> derived, but destruction goes from derived ->
> base.
> But if you add these tear down hooks into the mix, it violates that.  tear
> down hooks get invoked as part of TestBase.tearDown(), so in the above
> example the initialization order is 1 -> 2 -> 3 but the teardown order is 2
> -> 1 -> 3  (or 2 -> 3 -> 1, or none of the above depending on where inside
> of TestBase.tearDown() hook the hooks get invoked).
> To make matters worse, tear down hooks can be added from arbitrary points in
> a test's run, not just during setup.
> The only way I can see to fix this is to delete this tearDownHook mechanism
> entirely.  Anyone who wants it can easily reimplement this in the individual
> test by just keeping their own list of lambdas in the derived class,
> overriding tearDown(), and running through their own list in reverse order
> before calling TestBase.tearDown().
> I don't intend to do this work right now, but I would like to do it in the
> future, so I want to throw this out there and see if anyone has thoughts on
> it.
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