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Ovid (2709)

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Stuff with the Perl Foundation. A couple of patches in the Perl core. A few CPAN modules. That about sums it up.

Journal of Ovid (2709)

Thursday July 24, 2008
02:03 AM

Altering &Test::Most::explain?

[ #37004 ]

In Test::Most, I have an "explain" function. This functions just like &Test::More::diag, except it only triggers in verbose mode. Thus, if you run an individual test to see its full output, you see the "explain" dialogue. When you run a full test suite, you don't. It's very handy to keep from having "messy" test suite output.

Now I'm thinking about rewriting it as follows:

sub explain {
    return unless $ENV{TEST_VERBOSE};
    if ( ref $_[0] ) {
        require Data::Dumper;
        local $Data::Dumper::Indent   = 1;
        local $Data::Dumper::Sortkeys = 1;
    else {

In other words, you can forget about using Data::Dumper in your test suites just to diagnose bugs. You can do this:

my $self = Some::Object->new($id);
explain $self;

Since we rarely need to print a reference as a string, this seems right, but I wonder if I'm violating some principle of least surprise.

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  • .. but maybe you should even try to dump each ref in the argument list (untested):

    sub explain {
      return unless $ENV{TEST_VERBOSE};
          ref $_ ? do {
            require Data::Dumper;
            local $Data::Dumper::Indent   = 1;
  • I think it is such a good idea that I would plead for it to be moved into Test::More::diag. But as that is not likely, your idea is quite nifty og even nice.
  • After something like ten years of Perl, I still expect diag to dumper for me, so you won't be surprising me at all.