nysus has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to figure out why prove's --merge option gives me different output after running this test file: 

use strict;
use warnings;
use Test::More;

ok 1;
ok 0;

done_testing();

[download]

With --merge: 

> $ prove  --merge t/test.t                                           
+                                         
t/test.t .. Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/2 subtests

Test Summary Report
-------------------
t/test.t (Wstat: 256 (exited 1) Tests: 2 Failed: 1)
  Failed test:  2
  Non-zero exit status: 1
Files=1, Tests=2,  0 wallclock secs ( 0.01 usr  0.00 sys +  0.01 cusr 
+ 0.00 csys =  0.02 CPU)
Result: FAIL

[download]

And without: 

> $ prove  t/test.t                                                   
+                                          
t/test.t .. 1/?
#   Failed test at t/test.t line 6.
# Looks like you failed 1 test of 2.
t/test.t .. Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/2 subtests

Test Summary Report
-------------------
t/test.t (Wstat: 256 (exited 1) Tests: 2 Failed: 1)
  Failed test:  2
  Non-zero exit status: 1
Files=1, Tests=2,  0 wallclock secs ( 0.01 usr  0.00 sys +  0.01 cusr 
+ 0.00 csys =  0.02 CPU)
Result: FAIL

[download]

I get a more detailed report without merge. I'm not sure why. I thought merge was supposed to merge STDERR into STDOUT so I didn't think there should be a difference. Merge docs say:

--merge

If you need to make sure your diagnostics are displayed in the correct order relative to test results you can use the --merge option to merge the test scripts' STDERR into their STDOUT.

This guarantees that STDOUT (where the test results appear) and STDERR (where the diagnostics appear) will stay in sync. The harness will display any diagnostics your tests emit on STDERR.

Caveat: this is a bit of a kludge. In particular note that if anything that appears on STDERR looks like a test result the test harness will get confused. Use this option only if you understand the consequences and can live with the risk.

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$nysus = $PM . ' ' . $MC;
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Replies are listed 'Best First'.
Re: Getting less output using prove's --merge option
by choroba (Cardinal) on Feb 28, 2025 at 15:05 UTC
    I'm not sure what the problem is, but for non-MSWin, the culprit is this block: 
    else {
    $err = $merge ? '' : IO::Handle->new;
    eval { $pid = open3( '<&STDIN', $out, $err, @command ); };
    die "Could not execute (@command): $@" if $@;
    $sel = $merge ? undef : IO::Select->new( $out, $err );
}

    [download]

    What's going on there? Seems like $err is set to an empty string, which should create a new filehandle when calling open3. Then $sel is then set to undef, but I have no idea what that means.

    map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
[reply]
[d/l]
[select]
[reply]
[reply]
Re: Getting less output using prove's --merge option
by nysus (Parson) on Feb 28, 2025 at 14:34 UTC

    I just discovered that if I throw the -v option in there, the output is identical with or without --merge.

    $PM = "Perl Monk's";
    $MC = "Most Clueless Friar Abbot Bishop Pontiff Deacon Curate Priest Vicar Parson";
    $nysus = $PM . ' ' . $MC;
    Click here if you love Perl Monks

[reply]
[d/l]

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