1 # $Id: /mirror/googlecode/test-more/lib/Test/Tutorial.pod 57943 2008-08-18T02:09:22.275428Z brooklyn.kid51 $
4 Test::Tutorial - A tutorial about writing really basic tests
9 I<AHHHHHHH!!!! NOT TESTING! Anything but testing!
10 Beat me, whip me, send me to Detroit, but don't make
15 I<Besides, I don't know how to write the damned things.>
18 Is this you? Is writing tests right up there with writing
19 documentation and having your fingernails pulled out? Did you open up
22 ######## We start with some black magic
24 and decide that's quite enough for you?
26 It's ok. That's all gone now. We've done all the black magic for
27 you. And here are the tricks...
30 =head2 Nuts and bolts of testing.
32 Here's the most basic test program.
38 print 1 + 1 == 2 ? "ok 1\n" : "not ok 1\n";
40 since 1 + 1 is 2, it prints:
45 What this says is: C<1..1> "I'm going to run one test." [1] C<ok 1>
46 "The first test passed". And that's about all magic there is to
47 testing. Your basic unit of testing is the I<ok>. For each thing you
48 test, an C<ok> is printed. Simple. B<Test::Harness> interprets your test
49 results to determine if you succeeded or failed (more on that later).
51 Writing all these print statements rapidly gets tedious. Fortunately,
52 there's B<Test::Simple>. It has one function, C<ok()>.
56 use Test::Simple tests => 1;
60 and that does the same thing as the code above. C<ok()> is the backbone
61 of Perl testing, and we'll be using it instead of roll-your-own from
62 here on. If C<ok()> gets a true value, the test passes. False, it
67 use Test::Simple tests => 2;
76 # Failed test (test.pl at line 5)
77 # Looks like you failed 1 tests of 2.
79 C<1..2> "I'm going to run two tests." This number is used to ensure
80 your test program ran all the way through and didn't die or skip some
81 tests. C<ok 1> "The first test passed." C<not ok 2> "The second test
82 failed". Test::Simple helpfully prints out some extra commentary about
85 It's not scary. Come, hold my hand. We're going to give an example
86 of testing a module. For our example, we'll be testing a date
87 library, B<Date::ICal>. It's on CPAN, so download a copy and follow
91 =head2 Where to start?
93 This is the hardest part of testing, where do you start? People often
94 get overwhelmed at the apparent enormity of the task of testing a
95 whole module. Best place to start is at the beginning. Date::ICal is
96 an object-oriented module, and that means you start by making an
97 object. So we test C<new()>.
101 use Test::Simple tests => 2;
105 my $ical = Date::ICal->new; # create an object
106 ok( defined $ical ); # check that we got something
107 ok( $ical->isa('Date::ICal') ); # and it's the right class
109 run that and you should get:
115 congratulations, you've written your first useful test.
120 That output isn't terribly descriptive, is it? When you have two
121 tests you can figure out which one is #2, but what if you have 102?
123 Each test can be given a little descriptive name as the second
126 use Test::Simple tests => 2;
128 ok( defined $ical, 'new() returned something' );
129 ok( $ical->isa('Date::ICal'), " and it's the right class" );
134 ok 1 - new() returned something
135 ok 2 - and it's the right class
138 =head2 Test the manual
140 Simplest way to build up a decent testing suite is to just test what
141 the manual says it does. [3] Let's pull something out of the
142 L<Date::ICal/SYNOPSIS> and test that all its bits work.
146 use Test::Simple tests => 8;
150 $ical = Date::ICal->new( year => 1964, month => 10, day => 16,
151 hour => 16, min => 12, sec => 47,
154 ok( defined $ical, 'new() returned something' );
155 ok( $ical->isa('Date::ICal'), " and it's the right class" );
156 ok( $ical->sec == 47, ' sec()' );
157 ok( $ical->min == 12, ' min()' );
158 ok( $ical->hour == 16, ' hour()' );
159 ok( $ical->day == 17, ' day()' );
160 ok( $ical->month == 10, ' month()' );
161 ok( $ical->year == 1964, ' year()' );
163 run that and you get:
166 ok 1 - new() returned something
167 ok 2 - and it's the right class
172 # Failed test (- at line 16)
175 # Looks like you failed 1 tests of 8.
177 Whoops, a failure! [4] Test::Simple helpfully lets us know on what line
178 the failure occurred, but not much else. We were supposed to get 17,
179 but we didn't. What did we get?? Dunno. We'll have to re-run the
180 test in the debugger or throw in some print statements to find out.
182 Instead, we'll switch from B<Test::Simple> to B<Test::More>. B<Test::More>
183 does everything B<Test::Simple> does, and more! In fact, Test::More does
184 things I<exactly> the way Test::Simple does. You can literally swap
185 Test::Simple out and put Test::More in its place. That's just what
188 Test::More does more than Test::Simple. The most important difference
189 at this point is it provides more informative ways to say "ok".
190 Although you can write almost any test with a generic C<ok()>, it
191 can't tell you what went wrong. Instead, we'll use the C<is()>
192 function, which lets us declare that something is supposed to be the
193 same as something else:
197 use Test::More tests => 8;
201 $ical = Date::ICal->new( year => 1964, month => 10, day => 16,
202 hour => 16, min => 12, sec => 47,
205 ok( defined $ical, 'new() returned something' );
206 ok( $ical->isa('Date::ICal'), " and it's the right class" );
207 is( $ical->sec, 47, ' sec()' );
208 is( $ical->min, 12, ' min()' );
209 is( $ical->hour, 16, ' hour()' );
210 is( $ical->day, 17, ' day()' );
211 is( $ical->month, 10, ' month()' );
212 is( $ical->year, 1964, ' year()' );
214 "Is C<$ical-E<gt>sec> 47?" "Is C<$ical-E<gt>min> 12?" With C<is()> in place,
215 you get some more information
218 ok 1 - new() returned something
219 ok 2 - and it's the right class
224 # Failed test (- at line 16)
229 # Looks like you failed 1 tests of 8.
231 letting us know that C<$ical-E<gt>day> returned 16, but we expected 17. A
232 quick check shows that the code is working fine, we made a mistake
233 when writing up the tests. Just change it to:
235 is( $ical->day, 16, ' day()' );
237 and everything works.
239 So any time you're doing a "this equals that" sort of test, use C<is()>.
240 It even works on arrays. The test is always in scalar context, so you
241 can test how many elements are in a list this way. [5]
243 is( @foo, 5, 'foo has 5 elements' );
246 =head2 Sometimes the tests are wrong
248 Which brings us to a very important lesson. Code has bugs. Tests are
249 code. Ergo, tests have bugs. A failing test could mean a bug in the
250 code, but don't discount the possibility that the test is wrong.
252 On the flip side, don't be tempted to prematurely declare a test
253 incorrect just because you're having trouble finding the bug.
254 Invalidating a test isn't something to be taken lightly, and don't use
255 it as a cop out to avoid work.
258 =head2 Testing lots of values
260 We're going to be wanting to test a lot of dates here, trying to trick
261 the code with lots of different edge cases. Does it work before 1970?
262 After 2038? Before 1904? Do years after 10,000 give it trouble?
263 Does it get leap years right? We could keep repeating the code above,
264 or we could set up a little try/expect loop.
266 use Test::More tests => 32;
270 # An ICal string And the year, month, date
271 # hour, minute and second we expect.
272 '19971024T120000' => # from the docs.
273 [ 1997, 10, 24, 12, 0, 0 ],
274 '20390123T232832' => # after the Unix epoch
275 [ 2039, 1, 23, 23, 28, 32 ],
276 '19671225T000000' => # before the Unix epoch
277 [ 1967, 12, 25, 0, 0, 0 ],
278 '18990505T232323' => # before the MacOS epoch
279 [ 1899, 5, 5, 23, 23, 23 ],
283 while( my($ical_str, $expect) = each %ICal_Dates ) {
284 my $ical = Date::ICal->new( ical => $ical_str );
286 ok( defined $ical, "new(ical => '$ical_str')" );
287 ok( $ical->isa('Date::ICal'), " and it's the right class" );
289 is( $ical->year, $expect->[0], ' year()' );
290 is( $ical->month, $expect->[1], ' month()' );
291 is( $ical->day, $expect->[2], ' day()' );
292 is( $ical->hour, $expect->[3], ' hour()' );
293 is( $ical->min, $expect->[4], ' min()' );
294 is( $ical->sec, $expect->[5], ' sec()' );
297 So now we can test bunches of dates by just adding them to
298 C<%ICal_Dates>. Now that it's less work to test with more dates, you'll
299 be inclined to just throw more in as you think of them.
300 Only problem is, every time we add to that we have to keep adjusting
301 the C<use Test::More tests =E<gt> ##> line. That can rapidly get
302 annoying. There's two ways to make this work better.
304 First, we can calculate the plan dynamically using the C<plan()>
314 # For each key in the hash we're running 8 tests.
315 plan tests => keys %ICal_Dates * 8;
317 Or to be even more flexible, we use C<no_plan>. This means we're just
318 running some tests, don't know how many. [6]
320 use Test::More 'no_plan'; # instead of tests => 32
322 now we can just add tests and not have to do all sorts of math to
323 figure out how many we're running.
326 =head2 Informative names
328 Take a look at this line here
330 ok( defined $ical, "new(ical => '$ical_str')" );
332 we've added more detail about what we're testing and the ICal string
333 itself we're trying out to the name. So you get results like:
335 ok 25 - new(ical => '19971024T120000')
336 ok 26 - and it's the right class
344 if something in there fails, you'll know which one it was and that
345 will make tracking down the problem easier. So try to put a bit of
346 debugging information into the test names.
348 Describe what the tests test, to make debugging a failed test easier
349 for you or for the next person who runs your test.
352 =head2 Skipping tests
354 Poking around in the existing Date::ICal tests, I found this in
359 use Test::More tests => 7;
362 # Make sure epoch time is being handled sanely.
363 my $t1 = Date::ICal->new( epoch => 0 );
364 is( $t1->epoch, 0, "Epoch time of 0" );
366 # XXX This will only work on unix systems.
367 is( $t1->ical, '19700101Z', " epoch to ical" );
369 is( $t1->year, 1970, " year()" );
370 is( $t1->month, 1, " month()" );
371 is( $t1->day, 1, " day()" );
373 # like the tests above, but starting with ical instead of epoch
374 my $t2 = Date::ICal->new( ical => '19700101Z' );
375 is( $t2->ical, '19700101Z', "Start of epoch in ICal notation" );
377 is( $t2->epoch, 0, " and back to ICal" );
379 The beginning of the epoch is different on most non-Unix operating
380 systems [8]. Even though Perl smooths out the differences for the most
381 part, certain ports do it differently. MacPerl is one off the top of
382 my head. [9] We I<know> this will never work on MacOS. So rather than
383 just putting a comment in the test, we can explicitly say it's never
384 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.