[llvm-dev] Test Error Paths for Expected & ErrorOr

Stefan Gränitz via llvm-dev llvm-dev at lists.llvm.org
Thu Jul 27 08:54:20 PDT 2017

Yes definitely, testing a small piece of code like the
GlobPattern::create() example, it would mostly indicate missing unit
tests or insufficient test data.

In contrast to unit tests, however, it can also verify correct handling
of errors passed between function call hierarchies in more complex
For this I should point to the other example in the code, where it's
applied to llvm::object::createBinary():

Here it detects and runs 44 different control paths, that can hardly be
covered by a unit test altogether, because they don't depend on the
input to creatBinary() but rather on the environment the test runs in.

Am 27.07.17 um 16:46 schrieb David Blaikie:
> I /kind/ of like the idea - but it almost feels like this would be a
> tool for finding out that test coverage is insufficient, then adding
> tests that actually exercise the bad input, etc (this should be
> equally discoverable by code coverage, probably? Maybe not if multiple
> error paths all collapse together, maybe... )
> For instance, with your example, especially once there's an identified
> bug that helps motivate, would it not be better to add a test that
> does pass a fileName input that fails GlobPattern::create?
> On Thu, Jul 27, 2017 at 5:10 AM Stefan Gränitz via llvm-dev
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>     Hello, this is a call for feedback: opinions, improvements, testers..
>     I use the support classes Expected<T> and ErrorOr<T> quite often
>     recently and I like the concept a lot! Thanks Lang btw!
>     However, from time to time I found issues in the execution paths of my
>     error cases and got annoyed by their naturally low test coverage.
>     So I started sketching a test that runs all error paths for a given
>     piece of code to detect these issues. I just pushed it to GitHub and
>     added a little readme:
>     https://github.com/weliveindetail/ForceAllErrors-in-LLVM
>     Are there people on the list facing the same issue?
>     How do you test your error paths?
>     Could this be of use for you if it was in a reusable state?
>     Is there something similar already around?
>     Anyone seeing bugs or improvements?
>     Could it maybe even increase coverage in the LLVM test suite some day?
>     Thanks for all kinds of feedback!
>     Cheers, Stefan
>     --
>     https://weliveindetail.github.io/blog/
>     https://cryptup.org/pub/stefan.graenitz@gmail.com
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