Test::Differences(3) User Contributed Perl Documentation Test::Differences(3)NAMETest::Differences - Test strings and data structures and show
differences if not ok
VERSION
0.61
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.
These functions assume that you are presenting it with "flat" records,
looking like:
- scalars composed of record-per-line
- arrays of scalars,
- arrays of arrays of scalars,
- arrays of hashes containing only scalars
All of these are flattened in to single strings which are then compared
for differences. Differently data structures can be compared, as long
as they flatten identically.
All other data structures are run through Data::Dumper first. This is
a bit dangerous, as some versions of perl shipped with Data::Dumpers
that could do the oddest things with unexpected, like core dump. Only
as of 5.8.0 does Data::Dumper sort hash keys, which is necessary for
HASH dumps to be fully predictable. This will be changed when this
bites somebody or I get some free time.
"eq_or_diff()" starts counting records at 0 unless you pass it two text
strings:
eq_or_diff $a, $b; ## First line is line number 1
eq_or_diff @a, @b; ## First element is element 0
eq_or_diff $a, @b; ## First line/element is element 0
If you want to force a first record number of 0, use "eq_or_diff_data".
If you want to force a first record number of 1, use "eq_or_diff_text".
I chose this over passing in an options hash because it's clearer and
simpler this way. YMMV.
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". See "eq_or_diff_text" and "eq_or_diff_data" to
understand this. You can usually ignore this.
· "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.
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';
}
DEPLOYING
There are several basic ways of deploying Test::Differences requiring
more or less labor by you or your users.
· Fallback to "is_deeply".
This is your best option if you want this module to be optional.
use Test::More;
BEGIN {
if (!eval q{ use Test::Differences; 1 }) {
*eq_or_diff = \&is_deeply;
}
}
·
eval "use Test::Differences";
If you want to detect the presence of Test::Differences on the fly,
something like the following code might do the trick for you:
use Test qw( !ok ); ## get all syms *except* ok
eval "use Test::Differences";
use Data::Dumper;
sub ok {
goto &eq_or_diff if defined &eq_or_diff && @_ > 1;
@_ = map ref $_ ? Dumper( @_ ) : $_, @_;
goto Test::&ok;
}
plan tests => 1;
ok "a", "b";
· PREREQ_PM => { .... "Test::Differences" => 0, ... }
This method will let CPAN and CPANPLUS users download it
automatically. It will discomfit those users who choose/have to
download all packages manually.
· t/lib/Test/Differences.pm, t/lib/Text/Diff.pm, ...
By placing Test::Differences and its prerequisites in the t/lib
directory, you avoid forcing your users to download the
Test::Differences manually if they aren't using CPAN or CPANPLUS.
If you put a "use lib "t/lib";" in the top of each test suite
before the "use Test::Differences;", "make test" should work well.
You might want to check once in a while for new Test::Differences
releases if you do this.
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.
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.
AUTHOR
Barrie Slaymaker <barries@slaysys.com>
MAINTAINER
Curtis "Ovid" Poe <ovid@cpan.org>
LICENSE
Copyright 2001-2008 Barrie Slaymaker, All Rights Reserved.
You may use this software under the terms of the GNU public license,
any version, or the Artistic license.
perl v5.16.2 2013-08-25 Test::Differences(3)
