Re: [PATCH v2 1/2] test-lib: add a function to compare an expection with stdout from a command

From: Jeff King <peff@peff.net>
Date: Apr 17, 2016, 03:54 UTC
Message-ID: <20160417035414.GA30002@sigill.intra.peff.net>
In-Reply-To: <CAPig+cSOuFygsScGn_Nu0_d8mvRik1hQJuanrb-Nvw3ozyt7JQ@mail.gmail.com>

On Sat, Apr 16, 2016 at 11:07:02PM -0400, Eric Sunshine wrote:

Show 7 quoted lines

> > test_stdout accepts an expection and a command to execute.  It will execute
> > the command and then compare the stdout from that command to an expectation.
> > If the expectation is not met, a mock diff output is written to stderr.
> 
> I wonder if this deserves more flexibility by accepting a comparison
> operator, such as = and !=, similar to test_line_count()? Although, I
> suppose such functionality could be added later if deemed useful.

IMHO the funny syntax would outweigh the readability benefits. Unlike test_line_count(), which is abstracting a portability solution, this is mostly just about trying to save a few lines.

Though I do actually find that:

  test_stdout false git rev-parse --whatever

isn't great, because there's no syntactic separator between the expected output and the actual command to run. So I dunno, maybe it would be better as:

  test_stdout false = git rev-parse --whatever

and then you get "!=" for free later on if you want it.

We could also do:

  test_stdout git rev-parse --whatever <<-\EOF
  false
  EOF

which is more robust for multi-line output, but I think part of the point is to keep these as simple one-liners. You're not buying all that much over:

  cat >expect <<-\EOF &&
  false
  EOF
  git rev-parse --whatever >actual &&
  test_cmp expect actual

Though I do admit I've considered such a helper for some tests where that pattern is repeated ad nauseam.

Show 5 quoted lines

> > Based-on-a-patch-by: Jeff King <peff@peff.net>
> 
> Since Peff wrote the actual code[1], it might be worthwhile to give
> him authorship by prepending the commit message with a "From: Jeff
> King <peff@peff.net>" header.

Michael contacted me offline asking how to credit, and I actually suggested the "Based-on" route. I'm OK with it either way.

And for the record, my contribution is:

  Signed-off-by: Jeff King <peff@peff.net>

in case there are any DCO questions.

-Peff