plucky (3) Test::Differences.3pm.gz

Provided by: libtest-differences-perl_0.71-1_all bug

NAME

       Test::Differences - Test strings and data structures and show differences if not ok

SYNOPSIS

          use Test;    ## Or use Test::More
          use Test::Differences;

          eq_or_diff $got,  "a\nb\nc\n",   "testing strings";
          eq_or_diff \@got, [qw( a b c )], "testing arrays";

          ## Passing options:
          eq_or_diff $got, $expected, $name, { context => 300 };  ## options

          ## Using with DBI-like data structures

          use DBI;

          ... open connection & prepare statement and @expected_... here...

          eq_or_diff $sth->fetchall_arrayref, \@expected_arrays  "testing DBI arrays";
          eq_or_diff $sth->fetchall_hashref,  \@expected_hashes, "testing DBI hashes";

          ## To force textual or data line numbering (text lines are numbered 1..):
          eq_or_diff_text ...;
          eq_or_diff_data ...;

EXPORT

       This module exports three test functions and four diff-style functions:

       •   Test functions

           •   "eq_or_diff"

           •   "eq_or_diff_data"

           •   "eq_or_diff_text"

       •   Diff style functions

           •   "table_diff" (the default)

           •   "unified_diff"

           •   "oldstyle_diff"

           •   "context_diff"

DESCRIPTION

       When the code you're testing returns multiple lines, records or data structures and they're just plain
       wrong, an equivalent to the Unix "diff" utility may be just what's needed.  Here's output from an example
       test script that checks two text documents and then two (trivial) data structures:

        t/99example....1..3
        not ok 1 - differences in text
        #     Failed test ((eval 2) at line 14)
        #     +---+----------------+----------------+
        #     | Ln|Got             |Expected        |
        #     +---+----------------+----------------+
        #     |  1|this is line 1  |this is line 1  |
        #     *  2|this is line 2  |this is line b  *
        #     |  3|this is line 3  |this is line 3  |
        #     +---+----------------+----------------+
        not ok 2 - differences in whitespace
        #     Failed test ((eval 2) at line 20)
        #     +---+------------------+------------------+
        #     | Ln|Got               |Expected          |
        #     +---+------------------+------------------+
        #     |  1|        indented  |        indented  |
        #     *  2|        indented  |\tindented        *
        #     |  3|        indented  |        indented  |
        #     +---+------------------+------------------+
        not ok 3
        #     Failed test ((eval 2) at line 22)
        #     +----+-------------------------------------+----------------------------+
        #     | Elt|Got                                  |Expected                    |
        #     +----+-------------------------------------+----------------------------+
        #     *   0|bless( [                             |[                           *
        #     *   1|  'Move along, nothing to see here'  |  'Dry, humorless message'  *
        #     *   2|], 'Test::Builder' )                 |]                           *
        #     +----+-------------------------------------+----------------------------+
        # Looks like you failed 3 tests of 3.

       eq_or_diff_...() compares two strings or (limited) data structures and either emits an ok indication or a
       side-by-side diff.  Test::Differences is designed to be used with Test.pm and with Test::Simple,
       Test::More, and other Test::Builder based testing modules.  As the SYNOPSIS shows, another testing module
       must be used as the basis for your test suite.

OPTIONS

       The options to "eq_or_diff" give some fine-grained control over the output.

       •   "context"

           This allows you to control the amount of context shown:

              eq_or_diff $got, $expected, $name, { context => 50000 };

           will show you lots and lots of context.  Normally, eq_or_diff() uses some heuristics to determine
           whether to show 3 lines of context (like a normal unified diff) or 25 lines.

       •   "data_type"

           "text" or "data". This normally defaults to "data". If, however, neither of $got or $expected is a
           reference then  it defaults to "text". You can also force one or the other by calling
           "eq_or_diff_text" or "eq_or_diff_data".

           The difference is that in text mode lines are numbered from 1, but in data mode from 0 (and are
           refered to as 'elements' (Elt) instead of lines):

               # +---+-------+----------+
               # | Ln|Got    |Expected  |
               # +---+-------+----------+
               # *  1|'foo'  |'bar'     *
               # +---+-------+----------+

               # +----+---------+----+----------+
               # | Elt|Got      | Elt|Expected  |
               # +----+---------+----+----------+
               # *   0|[        *   0|'bar'     *
               # *   1|  'foo'  *    |          |
               # *   2|]        *    |          |
               # +----+---------+----+----------+

           The difference is purely cosmetic, it makes no difference to how comparisons are performed.

       •   "Sortkeys"

           If passed, whatever value is added is used as the argument for Data::Dumper Sortkeys option. See the
           Data::Dumper docs to understand how you can control the Sortkeys behavior.

       •   "filename_a" and "filename_b"

           The column headers to use in the output. They default to 'Got' and 'Expected'.

DIFF STYLES

       For extremely long strings, a table diff can wrap on your screen and be hard to read.  If you are
       comfortable with different diff formats, you can switch to a format more suitable for your data.  These
       are the four formats supported by the Text::Diff module and are set with the following functions:

       •   "table_diff" (the default)

       •   "unified_diff"

       •   "oldstyle_diff"

       •   "context_diff"

       You can run the following to understand the different diff output styles:

        use Test::More 'no_plan';
        use Test::Differences;

        my $long_string = join '' => 1..40;

        TODO: {
            local $TODO = 'Testing diff styles';

            # this is the default and does not need to explicitly set unless you need
            # to reset it back from another diff type
            table_diff;
            eq_or_diff $long_string, "-$long_string", 'table diff';

            unified_diff;
            eq_or_diff $long_string, "-$long_string", 'unified diff';

            context_diff;
            eq_or_diff $long_string, "-$long_string", 'context diff';

            oldstyle_diff;
            eq_or_diff $long_string, "-$long_string", 'oldstyle diff';
        }

UNICODE

       Generally you'll find that the following test output is disappointing.

           use Test::Differences;
           use utf8;

           my $want = { 'Traditional Chinese' => '中國' };
           my $have = { 'Traditional Chinese' => '中国' };

           eq_or_diff $have, $want, 'Unicode, baby';

       Here's what you get:

           #   Failed test 'Unicode, baby'
           #   at t/unicode.t line 12.
           # +----+-----------------------+-----------------------+
           # | Elt|Got                    |Expected               |
           # +----+-----------------------+-----------------------+
           # |   0|'Traditional Chinese'  |'Traditional Chinese'  |
           # *   1|'\x{4e2d}\x{56fd}'     |'\x{4e2d}\x{570b}'     *
           # +----+-----------------------+-----------------------+
           # Looks like you failed 1 test of 1.
           Dubious, test returned 1 (wstat 256, 0x100)
           Failed 1/1 subtests

       A patch to fix this would be *most* welcome.

Unknown::Values

       Unknown::Values is a module which provides values which will never compare as being the same as anything
       else, not even the same as itself.

       If code looks too hard at one of these values (and Test::Differences looks very hard indeed) that is a
       fatal error. This means that while we can detect the presence of these beasties, and tell you that they
       compare different, for Complicated Internals Reasons we can't show you much context. Sorry.

       NB that the support for these is experimental and relies on an undocumented unstable interface in
       Unknown::Values. If that fails then Test::Differences will probably just die when it sees them instead of
       telling you that the comparison failed.

LIMITATIONS

   "Test" or "Test::More"
       This module "mixes in" with Test.pm or any of the test libraries based on Test::Builder (Test::Simple,
       Test::More, etc).  It does this by peeking to see whether Test.pm or Test/Builder.pm is in %INC, so if
       you are not using one of those, it will print a warning and play dumb by not emitting test numbers (or
       incrementing them).  If you are using one of these, it should interoperate nicely.

   Exporting
       Exports all 3 functions by default (and by design).  Use

           use Test::Differences ();

       to suppress this behavior if you don't like the namespace pollution.

       This module will not override functions like ok(), is(), is_deeply(), etc.  If it did, then you could
       "eval "use Test::Differences qw( is_deeply );"" to get automatic upgrading to diffing behaviors without
       the "sub my_ok" shown above.  Test::Differences intentionally does not provide this behavior because this
       would mean that Test::Differences would need to emulate every popular test module out there, which would
       require far more coding and maintenance that I'm willing to do.  Use the eval and my_ok deployment shown
       above if you want some level of automation.

   Booleans
       Historically, true and false (whether resulting from logical-not "!" or from equality checks like "==")
       were represented in perl as numeric 1 for true and the empty string '' for false. In perl 5.36.0 they
       became real Boolean values which for backward compatibility also have their old numeric/string values. In
       5.38 (and in dev releases from 5.37.2 onwards) Data::Dumper belatedly learned about this, and so
       Test::Differences (which uses Data::Dumper under the bonnet) can also tell the difference.

       This means that `eq_or_diff(1, !!1)` will behave differently depending on whether you are using perl 5.38
       or later (in which case it will say they are different) or 5.36 or earlier (which will say they are the
       same).

   Unicode
       Perls before 5.6.0 don't support characters > 255 at all, and 5.6.0 seems broken.  This means that you
       might get odd results using perl5.6.0 with unicode strings.

   "Data::Dumper" and older Perls.
       Relies on Data::Dumper (for now), which, prior to perl5.8, will not always report hashes in the same
       order.   $Data::Dumper::Sortkeys  is set to 1, so on more recent versions of Data::Dumper, this should
       not occur.  Check CPAN to see if it's been peeled out of the main perl distribution and backported.
       Reported by Ilya Martynov <ilya@martynov.org>, although the Sortkeys "future perfect" workaround has been
       set in anticipation of a new Data::Dumper for a while.  Note that the two hashes should report the same
       here:

           not ok 5
           #     Failed test (t/ctrl/05-home.t at line 51)
           # +----+------------------------+----+------------------------+
           # | Elt|Got                     | Elt|Expected                |
           # +----+------------------------+----+------------------------+
           # |   0|{                       |   0|{                       |
           # |   1|  'password' => '',     |   1|  'password' => '',     |
           # *   2|  'method' => 'login',  *    |                        |
           # |   3|  'ctrl' => 'home',     |   2|  'ctrl' => 'home',     |
           # |    |                        *   3|  'method' => 'login',  *
           # |   4|  'email' => 'test'     |   4|  'email' => 'test'     |
           # |   5|}                       |   5|}                       |
           # +----+------------------------+----+------------------------+

       Data::Dumper also overlooks the difference between

           $a[0] = \$a[1];
           $a[1] = \$a[0];   # $a[0] = \$a[1]

       and

           $x = \$y;
           $y = \$x;
           @a = ( $x, $y );  # $a[0] = \$y, not \$a[1]

       The former involves two scalars, the latter 4: $x, $y, and @a[0,1].  This was carefully explained to me
       in words of two syllables or less by Yves Orton <demerphq@hotmail.com>.  The plan to address this is to
       allow you to select Data::Denter or some other module of your choice as an option.

   Code-refs
       Test::Differences turns on $Data::Dumper::Deparse, so any code-refs in your data structures will be
       turned into text before they are examined, using B::Deparse. The precise text generated for a sub-ref
       might not be what you expect as it is generated from the compiled version of the code, but it should at
       least be consistent and spot differences correctly.

       You can turn this behaviour off by setting $Test::Differences::NoDeparse.

AUTHORS

           Barrie Slaymaker <barries@slaysys.com> - original author

           Curtis "Ovid" Poe <ovid@cpan.org>

           David Cantrell <david@cantrell.org.uk>

LICENSE

       Copyright Barrie Slaymaker, Curtis "Ovid" Poe, and David Cantrell.

       All Rights Reserved.

       You may use, distribute and modify this software under the terms of the GNU public license, any version,
       or the Artistic license.