Re: [PATCH v2 1/1] contrib: add coverage-diff script

[Eric Sunshine <sunshine@sunshineco.com>]

On Thu, Sep 13, 2018 at 10:56 AM Derrick Stolee via GitGitGadget
<gitgitgadget@gmail.com> wrote:
> There have been a few bugs in recent patches what would have been caught
> if the test suite covered those blocks (including a few of mine). I want
> to work towards a "sensible" amount of coverage on new topics. In my opinion,
> this means that any logic should be covered, but the 'die()' blocks in error
> cases do not need to be covered.

The bit about die() blocks is perhaps a bit too general. While it's
true that some die()'s signal very unlikely (or near-impossible)
conditions, others are merely reporting invalid user or other input to
the program. The latter category is often very much worth testing, as
the number of test_must_fail() invocations in the test suite shows.
68a6b3a1bd (worktree: teach 'move' to override lock when --force given
twice, 2018-08-28), which was highlighted in your cover letter,
provides a good example of legitimately testing that a die() is
covered. So, perhaps the above can be toned-down a bit by saying
something like:

    ...but die() blocks covering very unlikely (or near-impossible)
    situations may not warrant coverage.

> It is important to not measure the coverage of the codebase by what old code
> is not covered.