NAME¶
Test::Differences - Test strings and data structures and show differences if not
ok
VERSION¶
0.62
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.
- •
- "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;
my $want = { 'Traditional Chinese' => 'XX' };
my $have = { 'Traditional Chinese' => 'XX' };
eq_or_diff $have, $want, 'Unicode, baby';
The output looks like this:
# Failed test 'Unicode, baby'
# at t/unicode.t line 12.
# +----+----------------------------+----------------------------+
# | Elt|Got |Expected |
# +----+----------------------------+----------------------------+
# | 0|'Traditional Chinese' |'Traditional Chinese' |
# * 1|'\xe4\xb8\xad\xe5\x9b\xbd' |'\xe4\xb8\xad\xe5\x9c\x8b' *
# +----+----------------------------+----------------------------+
# Looks like you failed 1 test of 1.
Dubious, test returned 1 (wstat 256, 0x100)
This is generally not helpful and someone points out that you didn't declare
your test program as being utf8, so you do that:
use Test::Differences;
use utf8;
my $want = { 'Traditional Chinese' => 'XX' };
my $have = { 'Traditional Chinese' => 'XX' };
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
That's better, but still awful. However, if you have "Text::Diff" 0.40
or higher installed, you can add this to your code:
BEGIN { $ENV{DIFF_OUTPUT_UNICODE} = 1 }
Make sure you do this
before you load Text::Diff. Then this is the
output:
# +----+-----------------------+-----------------------+
# | Elt|Got |Expected |
# +----+-----------------------+-----------------------+
# | 0|'Traditional Chinese' |'Traditional Chinese' |
# * 1|'XX' |'XX' *
# +----+-----------------------+-----------------------+
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.
AUTHORS¶
Barrie Slaymaker <barries@slaysys.com> - original author
Curtis "Ovid" Poe <ovid@cpan.org>
David Cantrell <david@cantrell.org.uk>
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.