1Differences(3) User Contributed Perl Documentation Differences(3)
2
6 Test::Differences - Test strings and data structures and show differ‐
7 ences if not ok
8
10 use Test; ## Or use Test::More
11 use Test::Differences;
12 eq_or_diff $got, "a\nb\nc\n", "testing strings";
14 eq_or_diff \@got, [qw( a b c )], "testing arrays";
15 ## Passing options:
17 eq_or_diff $got, $expected, $name, { context => 300 }; ## options
18 ## Using with DBI-like data structures
20 use DBI;
22 ... open connection & prepare statement and @expected_... here...
24 eq_or_diff $sth->fetchall_arrayref, \@expected_arrays "testing DBI arrays";
26 eq_or_diff $sth->fetchall_hashref, \@expected_hashes, "testing DBI hashes";
27 ## To force textual or data line numbering (text lines are numbered 1..):
29 eq_or_diff_text ...;
30 eq_or_diff_data ...;
31
33 When the code you're testing returns multiple lines, records or data
34 structures and they're just plain wrong, an equivalent to the Unix
35 "diff" utility may be just what's needed. Here's output from an exam‐
36 ple test script that checks two text documents and then two (trivial)
37 data structures:
38 t/99example....1..3
40 not ok 1 - differences in text
41 # Failed test ((eval 2) at line 14)
42 # +---+----------------+----------------+
43 # ⎪ Ln⎪Got ⎪Expected ⎪
44 # +---+----------------+----------------+
45 # ⎪ 1⎪this is line 1 ⎪this is line 1 ⎪
46 # * 2⎪this is line 2 ⎪this is line b *
47 # ⎪ 3⎪this is line 3 ⎪this is line 3 ⎪
48 # +---+----------------+----------------+
49 not ok 2 - differences in whitespace
50 # Failed test ((eval 2) at line 20)
51 # +---+------------------+------------------+
52 # ⎪ Ln⎪Got ⎪Expected ⎪
53 # +---+------------------+------------------+
54 # ⎪ 1⎪ indented ⎪ indented ⎪
55 # * 2⎪ indented ⎪\tindented *
56 # ⎪ 3⎪ indented ⎪ indented ⎪
57 # +---+------------------+------------------+
58 not ok 3
59 # Failed test ((eval 2) at line 22)
60 # +----+-------------------------------------+----------------------------+
61 # ⎪ Elt⎪Got ⎪Expected ⎪
62 # +----+-------------------------------------+----------------------------+
63 # * 0⎪bless( [ ⎪[ *
64 # * 1⎪ 'Move along, nothing to see here' ⎪ 'Dry, humorless message' *
65 # * 2⎪], 'Test::Builder' ) ⎪] *
66 # +----+-------------------------------------+----------------------------+
67 # Looks like you failed 3 tests of 3.
68 eq_or_diff_...() compares two strings or (limited) data structures and
70 either emits an ok indication or a side-by-side diff. Test::Differ‐
71 ences is designed to be used with Test.pm and with Test::Simple,
72 Test::More, and other Test::Builder based testing modules. As the SYN‐
73 OPSIS shows, another testing module must be used as the basis for your
74 test suite.
75 These functions assume that you are presenting it with "flat" records,
77 looking like:
78 - scalars composed of record-per-line
80 - arrays of scalars,
81 - arrays of arrays of scalars,
82 - arrays of hashes containing only scalars
83 All of these are flattened in to single strings which are then compared
85 for differences. Differently data structures can be compared, as long
86 as they flatten identically.
87 All other data structures are run through Data::Dumper first. This is
89 a bit dangerous, as some versions of perl shipped with Data::Dumpers
90 that could do the oddest things with unexpected, like core dump. Only
91 as of 5.8.0 does Data::Dumper sort hash keys, which is necessary for
92 HASH dumps to be fully predictable. This will be changed when this
93 bites somebody or I get some free time.
94 "eq_or_diff()" starts counting records at 0 unless you pass it two text
96 strings:
97 eq_or_diff $a, $b; ## First line is line number 1
99 eq_or_diff @a, @b; ## First element is element 0
100 eq_or_diff $a, @b; ## First line/element is element 0
101 If you want to force a first record number of 0, use "eq_or_diff_data".
103 If you want to force a first record number of 1, use "eq_or_diff_text".
104 I chose this over passing in an options hash because it's clearer and
105 simpler this way. YMMV.
106
108 There is currently only one option: "context". This allows you to con‐
109 trol the amount of context shown:
110 eq_or_diff $got, $expected, $name, { context => 50000};
112 will show you lots and lots of context. Normally, eq_or_diff() uses
114 some heuristics to determine whether to show 3 lines of context (like a
115 normal unified diff) or 25 lines (for
116
118 There are three basic ways of deploying Test::Differences requiring
119 more or less labor by you or your users.
120 · eval "use Test::Differences";
122 This is the easiest option.
124 If you want to detect the presence of Test::Differences on the fly,
126 something like the following code might do the trick for you:
127 use Test qw( !ok ); ## get all syms *except* ok
129 eval "use Test::Differences";
131 use Data::Dumper;
132 sub ok {
134 goto &eq_or_diff if defined &eq_or_diff && @_ > 1;
135 @_ = map ref $_ ? Dumper( @_ ) : $_, @_;
136 goto Test::&ok;
137 }
138 plan tests => 1;
140 ok "a", "b";
142 · PREREQ_PM => { .... "Test::Differences" => 0, ... }
144 This method will let CPAN and CPANPLUS users download it automati‐
146 cally. It will discomfit those users who choose/have to download
147 all packages manually.
148 · t/lib/Test/Differences.pm, t/lib/Text/Diff.pm, ...
150 By placing Test::Differences and it's prerequisites in the t/lib
152 directory, you avoid forcing your users to download the Test::Dif‐
153 ferences manually if they aren't using CPAN or CPANPLUS.
154 If you put a "use lib "t/lib";" in the top of each test suite
156 before the "use Test::Differences;", "make test" should work well.
157 You might want to check once in a while for new Test::Differences
159 releases if you do this.
160
162 This module "mixes in" with Test.pm or any of the test libraries based
163 on Test::Builder (Test::Simple, Test::More, etc). It does this by
164 peeking to see whether Test.pm or Test/Builder.pm is in %INC, so if you
165 are not using one of those, it will print a warning and play dumb by
166 not emitting test numbers (or incrementing them). If you are using one
167 of these, it should interoperate nicely.
168 Uses Data::Dumper for complex data structures (like hashes :), which
170 can lead to some problems on older perls.
171 Exports all 3 functions by default (and by design). Use
173 use Test::Differences ();
175 to suppress this behavior if you don't like the namespace pollution.
177 This module will not override functions like ok(), is(), is_deeply(),
179 etc. If it did, then you could "eval "use Test::Differences qw(
180 is_deeply );"" to get automatic upgrading to diffing behaviors without
181 the "sub my_ok" shown above. Test::Differences intentionally does not
182 provide this behavior because this would mean that Test::Differences
183 would need to emulate every popular test module out there, which would
184 require far more coding and maintenance that I'm willing to do. Use
185 the eval and my_ok deployment shown above if you want some level of au‐
186 tomation.
187
189 Perls before 5.6.0 don't support characters > 255 at all, and 5.6.0
190 seems broken. This means that you might get odd results using
191 perl5.6.0 with unicode strings.
192 Relies on Data::Dumper (for now), which, prior to perl5.8, will not
194 always report hashes in the same order. $Data::Dumper::SortKeys is
195 set to 1, so on more recent versions of Data::Dumper, this should not
196 occur. Check CPAN to see if it's been peeled out of the main perl dis‐
197 tribution and backported. Reported by Ilya Martynov <ilya@mar‐
198 tynov.org>, although the SortKeys "future perfect" workaround has been
199 set in anticipation of a new Data::Dumper for a while. Note that the
200 two hashes should report the same here:
201 not ok 5
203 # Failed test (t/ctrl/05-home.t at line 51)
204 # +----+------------------------+----+------------------------+
205 # ⎪ Elt⎪Got ⎪ Elt⎪Expected ⎪
206 # +----+------------------------+----+------------------------+
207 # ⎪ 0⎪{ ⎪ 0⎪{ ⎪
208 # ⎪ 1⎪ 'password' => '', ⎪ 1⎪ 'password' => '', ⎪
209 # * 2⎪ 'method' => 'login', * ⎪ ⎪
210 # ⎪ 3⎪ 'ctrl' => 'home', ⎪ 2⎪ 'ctrl' => 'home', ⎪
211 # ⎪ ⎪ * 3⎪ 'method' => 'login', *
212 # ⎪ 4⎪ 'email' => 'test' ⎪ 4⎪ 'email' => 'test' ⎪
213 # ⎪ 5⎪} ⎪ 5⎪} ⎪
214 # +----+------------------------+----+------------------------+
215 Data::Dumper also overlooks the difference between
217 $a[0] = \$a[1];
219 $a[1] = \$a[0]; # $a[0] = \$a[1]
220 and
222 $x = \$y;
224 $y = \$x;
225 @a = ( $x, $y ); # $a[0] = \$y, not \$a[1]
226 The former involves two scalars, the latter 4: $x, $y, and @a[0,1].
228 This was carefully explained to me in words of two syllables or less by
229 Yves Orton <demerphq@hotmail.com>. The plan to address this is to
230 allow you to select Data::Denter or some other module of your choice as
231 an option.
232
234 Barrie Slaymaker <barries@slaysys.com>
235
237 Copyright 2001 Barrie Slaymaker, All Rights Reserved.
238 You may use this software under the terms of the GNU public license,
240 any version, or the Artistic license.
241perl v5.8.8 2003-06-16 Differences(3)