3 Test::Tutorial - A tutorial about writing really basic tests
8 I<AHHHHHHH!!!! NOT TESTING! Anything but testing!
9 Beat me, whip me, send me to Detroit, but don't make
14 I<Besides, I don't know how to write the damned things.>
17 Is this you? Is writing tests right up there with writing
18 documentation and having your fingernails pulled out? Did you open up
21 ######## We start with some black magic
23 and decide that's quite enough for you?
25 It's ok. That's all gone now. We've done all the black magic for
26 you. And here are the tricks...
29 =head2 Nuts and bolts of testing.
31 Here's the most basic test program.
37 print 1 + 1 == 2 ? "ok 1\n" : "not ok 1\n";
39 since 1 + 1 is 2, it prints:
44 What this says is: C<1..1> "I'm going to run one test." [1] C<ok 1>
45 "The first test passed". And that's about all magic there is to
46 testing. Your basic unit of testing is the I<ok>. For each thing you
47 test, an C<ok> is printed. Simple. B<Test::Harness> interprets your test
48 results to determine if you succeeded or failed (more on that later).
50 Writing all these print statements rapidly gets tedious. Fortunately,
51 there's B<Test::Simple>. It has one function, C<ok()>.
55 use Test::Simple tests => 1;
59 and that does the same thing as the code above. C<ok()> is the backbone
60 of Perl testing, and we'll be using it instead of roll-your-own from
61 here on. If C<ok()> gets a true value, the test passes. False, it
66 use Test::Simple tests => 2;
75 # Failed test (test.pl at line 5)
76 # Looks like you failed 1 tests of 2.
78 C<1..2> "I'm going to run two tests." This number is used to ensure
79 your test program ran all the way through and didn't die or skip some
80 tests. C<ok 1> "The first test passed." C<not ok 2> "The second test
81 failed". Test::Simple helpfully prints out some extra commentary about
84 It's not scary. Come, hold my hand. We're going to give an example
85 of testing a module. For our example, we'll be testing a date
86 library, B<Date::ICal>. It's on CPAN, so download a copy and follow
90 =head2 Where to start?
92 This is the hardest part of testing, where do you start? People often
93 get overwhelmed at the apparent enormity of the task of testing a
94 whole module. Best place to start is at the beginning. Date::ICal is
95 an object-oriented module, and that means you start by making an
96 object. So we test C<new()>.
100 use Test::Simple tests => 2;
104 my $ical = Date::ICal->new; # create an object
105 ok( defined $ical ); # check that we got something
106 ok( $ical->isa('Date::ICal') ); # and it's the right class
108 run that and you should get:
114 congratulations, you've written your first useful test.
119 That output isn't terribly descriptive, is it? When you have two
120 tests you can figure out which one is #2, but what if you have 102?
122 Each test can be given a little descriptive name as the second
125 use Test::Simple tests => 2;
127 ok( defined $ical, 'new() returned something' );
128 ok( $ical->isa('Date::ICal'), " and it's the right class" );
133 ok 1 - new() returned something
134 ok 2 - and it's the right class
137 =head2 Test the manual
139 Simplest way to build up a decent testing suite is to just test what
140 the manual says it does. [3] Let's pull something out of the
141 L<Date::ICal/SYNOPSIS> and test that all its bits work.
145 use Test::Simple tests => 8;
149 $ical = Date::ICal->new( year => 1964, month => 10, day => 16,
150 hour => 16, min => 12, sec => 47,
153 ok( defined $ical, 'new() returned something' );
154 ok( $ical->isa('Date::ICal'), " and it's the right class" );
155 ok( $ical->sec == 47, ' sec()' );
156 ok( $ical->min == 12, ' min()' );
157 ok( $ical->hour == 16, ' hour()' );
158 ok( $ical->day == 17, ' day()' );
159 ok( $ical->month == 10, ' month()' );
160 ok( $ical->year == 1964, ' year()' );
162 run that and you get:
165 ok 1 - new() returned something
166 ok 2 - and it's the right class
171 # Failed test (- at line 16)
174 # Looks like you failed 1 tests of 8.
176 Whoops, a failure! [4] Test::Simple helpfully lets us know on what line
177 the failure occurred, but not much else. We were supposed to get 17,
178 but we didn't. What did we get?? Dunno. We'll have to re-run the
179 test in the debugger or throw in some print statements to find out.
181 Instead, we'll switch from B<Test::Simple> to B<Test::More>. B<Test::More>
182 does everything B<Test::Simple> does, and more! In fact, Test::More does
183 things I<exactly> the way Test::Simple does. You can literally swap
184 Test::Simple out and put Test::More in its place. That's just what
187 Test::More does more than Test::Simple. The most important difference
188 at this point is it provides more informative ways to say "ok".
189 Although you can write almost any test with a generic C<ok()>, it
190 can't tell you what went wrong. Instead, we'll use the C<is()>
191 function, which lets us declare that something is supposed to be the
192 same as something else:
196 use Test::More tests => 8;
200 $ical = Date::ICal->new( year => 1964, month => 10, day => 16,
201 hour => 16, min => 12, sec => 47,
204 ok( defined $ical, 'new() returned something' );
205 ok( $ical->isa('Date::ICal'), " and it's the right class" );
206 is( $ical->sec, 47, ' sec()' );
207 is( $ical->min, 12, ' min()' );
208 is( $ical->hour, 16, ' hour()' );
209 is( $ical->day, 17, ' day()' );
210 is( $ical->month, 10, ' month()' );
211 is( $ical->year, 1964, ' year()' );
213 "Is C<$ical-E<gt>sec> 47?" "Is C<$ical-E<gt>min> 12?" With C<is()> in place,
214 you get some more information
217 ok 1 - new() returned something
218 ok 2 - and it's the right class
223 # Failed test (- at line 16)
228 # Looks like you failed 1 tests of 8.
230 letting us know that C<$ical-E<gt>day> returned 16, but we expected 17. A
231 quick check shows that the code is working fine, we made a mistake
232 when writing up the tests. Just change it to:
234 is( $ical->day, 16, ' day()' );
236 and everything works.
238 So any time you're doing a "this equals that" sort of test, use C<is()>.
239 It even works on arrays. The test is always in scalar context, so you
240 can test how many elements are in a list this way. [5]
242 is( @foo, 5, 'foo has 5 elements' );
245 =head2 Sometimes the tests are wrong
247 Which brings us to a very important lesson. Code has bugs. Tests are
248 code. Ergo, tests have bugs. A failing test could mean a bug in the
249 code, but don't discount the possibility that the test is wrong.
251 On the flip side, don't be tempted to prematurely declare a test
252 incorrect just because you're having trouble finding the bug.
253 Invalidating a test isn't something to be taken lightly, and don't use
254 it as a cop out to avoid work.
257 =head2 Testing lots of values
259 We're going to be wanting to test a lot of dates here, trying to trick
260 the code with lots of different edge cases. Does it work before 1970?
261 After 2038? Before 1904? Do years after 10,000 give it trouble?
262 Does it get leap years right? We could keep repeating the code above,
263 or we could set up a little try/expect loop.
265 use Test::More tests => 32;
269 # An ICal string And the year, month, day
270 # hour, minute and second we expect.
271 '19971024T120000' => # from the docs.
272 [ 1997, 10, 24, 12, 0, 0 ],
273 '20390123T232832' => # after the Unix epoch
274 [ 2039, 1, 23, 23, 28, 32 ],
275 '19671225T000000' => # before the Unix epoch
276 [ 1967, 12, 25, 0, 0, 0 ],
277 '18990505T232323' => # before the MacOS epoch
278 [ 1899, 5, 5, 23, 23, 23 ],
282 while( my($ical_str, $expect) = each %ICal_Dates ) {
283 my $ical = Date::ICal->new( ical => $ical_str );
285 ok( defined $ical, "new(ical => '$ical_str')" );
286 ok( $ical->isa('Date::ICal'), " and it's the right class" );
288 is( $ical->year, $expect->[0], ' year()' );
289 is( $ical->month, $expect->[1], ' month()' );
290 is( $ical->day, $expect->[2], ' day()' );
291 is( $ical->hour, $expect->[3], ' hour()' );
292 is( $ical->min, $expect->[4], ' min()' );
293 is( $ical->sec, $expect->[5], ' sec()' );
296 So now we can test bunches of dates by just adding them to
297 C<%ICal_Dates>. Now that it's less work to test with more dates, you'll
298 be inclined to just throw more in as you think of them.
299 Only problem is, every time we add to that we have to keep adjusting
300 the C<use Test::More tests =E<gt> ##> line. That can rapidly get
301 annoying. There's two ways to make this work better.
303 First, we can calculate the plan dynamically using the C<plan()>
313 # For each key in the hash we're running 8 tests.
314 plan tests => keys(%ICal_Dates) * 8;
316 ...and then your tests...
318 Or to be even more flexible, we use C<no_plan>. This means we're just
319 running some tests, don't know how many. [6]
321 use Test::More 'no_plan'; # instead of tests => 32
323 now we can just add tests and not have to do all sorts of math to
324 figure out how many we're running.
327 =head2 Informative names
329 Take a look at this line here
331 ok( defined $ical, "new(ical => '$ical_str')" );
333 we've added more detail about what we're testing and the ICal string
334 itself we're trying out to the name. So you get results like:
336 ok 25 - new(ical => '19971024T120000')
337 ok 26 - and it's the right class
345 if something in there fails, you'll know which one it was and that
346 will make tracking down the problem easier. So try to put a bit of
347 debugging information into the test names.
349 Describe what the tests test, to make debugging a failed test easier
350 for you or for the next person who runs your test.
353 =head2 Skipping tests
355 Poking around in the existing Date::ICal tests, I found this in
360 use Test::More tests => 7;
363 # Make sure epoch time is being handled sanely.
364 my $t1 = Date::ICal->new( epoch => 0 );
365 is( $t1->epoch, 0, "Epoch time of 0" );
367 # XXX This will only work on unix systems.
368 is( $t1->ical, '19700101Z', " epoch to ical" );
370 is( $t1->year, 1970, " year()" );
371 is( $t1->month, 1, " month()" );
372 is( $t1->day, 1, " day()" );
374 # like the tests above, but starting with ical instead of epoch
375 my $t2 = Date::ICal->new( ical => '19700101Z' );
376 is( $t2->ical, '19700101Z', "Start of epoch in ICal notation" );
378 is( $t2->epoch, 0, " and back to ICal" );
380 The beginning of the epoch is different on most non-Unix operating
381 systems [8]. Even though Perl smooths out the differences for the
382 most part, certain ports do it differently. MacPerl is one off the
383 top of my head. [9] So rather than just putting a comment in the test,
384 we can explicitly say it's never going to work and skip the test.
386 use Test::More tests => 7;
389 # Make sure epoch time is being handled sanely.
390 my $t1 = Date::ICal->new( epoch => 0 );
391 is( $t1->epoch, 0, "Epoch time of 0" );
394 skip('epoch to ICal not working on MacOS', 6)
397 is( $t1->ical, '19700101Z', " epoch to ical" );
399 is( $t1->year, 1970, " year()" );
400 is( $t1->month, 1, " month()" );
401 is( $t1->day, 1, " day()" );
403 # like the tests above, but starting with ical instead of epoch
404 my $t2 = Date::ICal->new( ical => '19700101Z' );
405 is( $t2->ical, '19700101Z', "Start of epoch in ICal notation" );
407 is( $t2->epoch, 0, " and back to ICal" );
410 A little bit of magic happens here. When running on anything but
411 MacOS, all the tests run normally. But when on MacOS, C<skip()> causes
412 the entire contents of the SKIP block to be jumped over. It's never
413 run. Instead, it prints special output that tells Test::Harness that
414 the tests have been skipped.
417 ok 1 - Epoch time of 0
418 ok 2 # skip epoch to ICal not working on MacOS
419 ok 3 # skip epoch to ICal not working on MacOS
420 ok 4 # skip epoch to ICal not working on MacOS
421 ok 5 # skip epoch to ICal not working on MacOS
422 ok 6 # skip epoch to ICal not working on MacOS
423 ok 7 # skip epoch to ICal not working on MacOS
425 This means your tests won't fail on MacOS. This means less emails
426 from MacPerl users telling you about failing tests that you know will
427 never work. You've got to be careful with skip tests. These are for
428 tests which don't work and I<never will>. It is not for skipping
429 genuine bugs (we'll get to that in a moment).
431 The tests are wholly and completely skipped. [10] This will work.
434 skip("I don't wanna die!");
436 die, die, die, die, die;
442 Thumbing through the Date::ICal man page, I came across this:
446 $ical_string = $ical->ical;
448 Retrieves, or sets, the date on the object, using any
449 valid ICal date/time string.
451 "Retrieves or sets". Hmmm, didn't see a test for using C<ical()> to set
452 the date in the Date::ICal test suite. So I'll write one.
454 use Test::More tests => 1;
457 my $ical = Date::ICal->new;
458 $ical->ical('20201231Z');
459 is( $ical->ical, '20201231Z', 'Setting via ical()' );
464 not ok 1 - Setting via ical()
465 # Failed test (- at line 6)
466 # got: '20010814T233649Z'
467 # expected: '20201231Z'
468 # Looks like you failed 1 tests of 1.
470 Whoops! Looks like it's unimplemented. Let's assume we don't have
471 the time to fix this. [11] Normally, you'd just comment out the test
472 and put a note in a todo list somewhere. Instead, we're going to
473 explicitly state "this test will fail" by wrapping it in a C<TODO> block.
475 use Test::More tests => 1;
478 local $TODO = 'ical($ical) not yet implemented';
480 my $ical = Date::ICal->new;
481 $ical->ical('20201231Z');
483 is( $ical->ical, '20201231Z', 'Setting via ical()' );
486 Now when you run, it's a little different:
489 not ok 1 - Setting via ical() # TODO ical($ical) not yet implemented
490 # got: '20010822T201551Z'
491 # expected: '20201231Z'
493 Test::More doesn't say "Looks like you failed 1 tests of 1". That '#
494 TODO' tells Test::Harness "this is supposed to fail" and it treats a
495 failure as a successful test. So you can write tests even before
496 you've fixed the underlying code.
498 If a TODO test passes, Test::Harness will report it "UNEXPECTEDLY
499 SUCCEEDED". When that happens, you simply remove the TODO block with
500 C<local $TODO> and turn it into a real test.
503 =head2 Testing with taint mode.
505 Taint mode is a funny thing. It's the globalest of all global
506 features. Once you turn it on, it affects I<all> code in your program
507 and I<all> modules used (and all the modules they use). If a single
508 piece of code isn't taint clean, the whole thing explodes. With that
509 in mind, it's very important to ensure your module works under taint
512 It's very simple to have your tests run under taint mode. Just throw
513 a C<-T> into the C<#!> line. Test::Harness will read the switches
514 in C<#!> and use them to run your tests.
518 ...test normally here...
520 So when you say C<make test> it will be run with taint mode and
530 The first number doesn't really mean anything, but it has to be 1.
531 It's the second number that's important.
535 For those following along at home, I'm using version 1.31. It has
536 some bugs, which is good -- we'll uncover them with our tests.
540 You can actually take this one step further and test the manual
541 itself. Have a look at B<Test::Inline> (formerly B<Pod::Tests>).
545 Yes, there's a mistake in the test suite. What! Me, contrived?
549 We'll get to testing the contents of lists later.
553 But what happens if your test program dies halfway through?! Since we
554 didn't say how many tests we're going to run, how can we know it
555 failed? No problem, Test::More employs some magic to catch that death
556 and turn the test into a failure, even if every test passed up to that
561 I cleaned it up a little.
565 Most Operating Systems record time as the number of seconds since a
566 certain date. This date is the beginning of the epoch. Unix's starts
567 at midnight January 1st, 1970 GMT.
571 MacOS's epoch is midnight January 1st, 1904. VMS's is midnight,
572 November 17th, 1858, but vmsperl emulates the Unix epoch so it's not a
577 As long as the code inside the SKIP block at least compiles. Please
578 don't ask how. No, it's not a filter.
582 Do NOT be tempted to use TODO tests as a way to avoid fixing simple
589 Michael G Schwern E<lt>schwern@pobox.comE<gt> and the perl-qa dancers!
593 Copyright 2001 by Michael G Schwern E<lt>schwern@pobox.comE<gt>.
595 This documentation is free; you can redistribute it and/or modify it
596 under the same terms as Perl itself.
598 Irrespective of its distribution, all code examples in these files
599 are hereby placed into the public domain. You are permitted and
600 encouraged to use this code in your own programs for fun
601 or for profit as you see fit. A simple comment in the code giving
602 credit would be courteous but is not required.