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

•

Diff style functions

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¶

    use Test::Differences ();

    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|}                       |
    # +----+------------------------+----+------------------------+

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

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

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.