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1 | =head1 NAME |
2 | |
3 | Test::Tutorial - A tutorial about writing really basic tests |
4 | |
5 | =head1 DESCRIPTION |
6 | |
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7 | |
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8 | I<AHHHHHHH!!!! NOT TESTING! Anything but testing! |
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9 | Beat me, whip me, send me to Detroit, but don't make |
10 | me write tests!> |
11 | |
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12 | I<*sob*> |
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13 | |
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14 | I<Besides, I don't know how to write the damned things.> |
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15 | |
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16 | |
17 | Is this you? Is writing tests right up there with writing |
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18 | documentation and having your fingernails pulled out? Did you open up |
19 | a test and read |
20 | |
21 | ######## We start with some black magic |
22 | |
23 | and decide that's quite enough for you? |
24 | |
25 | It's ok. That's all gone now. We've done all the black magic for |
26 | you. And here are the tricks... |
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27 | |
28 | |
29 | =head2 Nuts and bolts of testing. |
30 | |
31 | Here's the most basic test program. |
32 | |
33 | #!/usr/bin/perl -w |
34 | |
35 | print "1..1\n"; |
36 | |
37 | print 1 + 1 == 2 ? "ok 1\n" : "not ok 1\n"; |
38 | |
39 | since 1 + 1 is 2, it prints: |
40 | |
41 | 1..1 |
42 | ok 1 |
43 | |
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 |
4bd4e70a |
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 |
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48 | results to determine if you succeeded or failed (more on that later). |
49 | |
50 | Writing all these print statements rapidly gets tedious. Fortunately, |
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51 | there's B<Test::Simple>. It has one function, C<ok()>. |
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52 | |
53 | #!/usr/bin/perl -w |
54 | |
55 | use Test::Simple tests => 1; |
56 | |
57 | ok( 1 + 1 == 2 ); |
58 | |
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59 | and that does the same thing as the code above. C<ok()> is the backbone |
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60 | of Perl testing, and we'll be using it instead of roll-your-own from |
4bd4e70a |
61 | here on. If C<ok()> gets a true value, the test passes. False, it |
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62 | fails. |
63 | |
64 | #!/usr/bin/perl -w |
65 | |
66 | use Test::Simple tests => 2; |
67 | ok( 1 + 1 == 2 ); |
68 | ok( 2 + 2 == 5 ); |
69 | |
70 | from that comes |
71 | |
72 | 1..2 |
73 | ok 1 |
74 | not ok 2 |
75 | # Failed test (test.pl at line 5) |
76 | # Looks like you failed 1 tests of 2. |
77 | |
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 |
4bd4e70a |
81 | failed". Test::Simple helpfully prints out some extra commentary about |
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82 | your tests. |
83 | |
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 |
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86 | library, B<Date::ICal>. It's on CPAN, so download a copy and follow |
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87 | along. [2] |
88 | |
89 | |
90 | =head2 Where to start? |
91 | |
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 |
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96 | object. So we test C<new()>. |
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97 | |
98 | #!/usr/bin/perl -w |
99 | |
100 | use Test::Simple tests => 2; |
101 | |
102 | use Date::ICal; |
103 | |
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 |
107 | |
108 | run that and you should get: |
109 | |
110 | 1..2 |
111 | ok 1 |
112 | ok 2 |
113 | |
114 | congratulations, you've written your first useful test. |
115 | |
116 | |
117 | =head2 Names |
118 | |
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? |
121 | |
122 | Each test can be given a little descriptive name as the second |
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123 | argument to C<ok()>. |
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124 | |
125 | use Test::Simple tests => 2; |
126 | |
127 | ok( defined $ical, 'new() returned something' ); |
128 | ok( $ical->isa('Date::ICal'), " and it's the right class" ); |
129 | |
130 | So now you'd see... |
131 | |
132 | 1..2 |
133 | ok 1 - new() returned something |
134 | ok 2 - and it's the right class |
135 | |
136 | |
137 | =head2 Test the manual |
138 | |
139 | Simplest way to build up a decent testing suite is to just test what |
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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. |
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142 | |
143 | #!/usr/bin/perl -w |
144 | |
145 | use Test::Simple tests => 8; |
146 | |
147 | use Date::ICal; |
148 | |
149 | $ical = Date::ICal->new( year => 1964, month => 10, day => 16, |
150 | hour => 16, min => 12, sec => 47, |
151 | tz => '0530' ); |
152 | |
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()' ); |
161 | |
162 | run that and you get: |
163 | |
164 | 1..8 |
165 | ok 1 - new() returned something |
166 | ok 2 - and it's the right class |
167 | ok 3 - sec() |
168 | ok 4 - min() |
169 | ok 5 - hour() |
170 | not ok 6 - day() |
171 | # Failed test (- at line 16) |
172 | ok 7 - month() |
173 | ok 8 - year() |
174 | # Looks like you failed 1 tests of 8. |
175 | |
176 | Whoops, a failure! [4] Test::Simple helpfully lets us know on what line |
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177 | the failure occurred, but not much else. We were supposed to get 17, |
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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. |
180 | |
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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 |
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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 |
185 | we're going to do. |
186 | |
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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: |
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193 | |
194 | #!/usr/bin/perl -w |
195 | |
196 | use Test::More tests => 8; |
197 | |
198 | use Date::ICal; |
199 | |
200 | $ical = Date::ICal->new( year => 1964, month => 10, day => 16, |
201 | hour => 16, min => 12, sec => 47, |
202 | tz => '0530' ); |
203 | |
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( $ical->year, 1964, ' year()' ); |
212 | |
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213 | "Is C<$ical-E<gt>sec> 47?" "Is C<$ical-E<gt>min> 12?" With C<is()> in place, |
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214 | you get some more information |
215 | |
216 | 1..8 |
217 | ok 1 - new() returned something |
218 | ok 2 - and it's the right class |
219 | ok 3 - sec() |
220 | ok 4 - min() |
221 | ok 5 - hour() |
222 | not ok 6 - day() |
223 | # Failed test (- at line 16) |
224 | # got: '16' |
225 | # expected: '17' |
226 | ok 7 - month() |
227 | ok 8 - year() |
228 | # Looks like you failed 1 tests of 8. |
229 | |
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230 | letting us know that C<$ical-E<gt>day> returned 16, but we expected 17. A |
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231 | quick check shows that the code is working fine, we made a mistake |
232 | when writing up the tests. Just change it to: |
233 | |
234 | is( $ical->day, 16, ' day()' ); |
235 | |
236 | and everything works. |
237 | |
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238 | So any time you're doing a "this equals that" sort of test, use C<is()>. |
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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] |
241 | |
242 | is( @foo, 5, 'foo has 5 elements' ); |
243 | |
244 | |
245 | =head2 Sometimes the tests are wrong |
246 | |
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. |
250 | |
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. |
255 | |
256 | |
257 | =head2 Testing lots of values |
258 | |
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. |
264 | |
265 | use Test::More tests => 32; |
266 | use Date::ICal; |
267 | |
268 | my %ICal_Dates = ( |
269 | # An ICal string And the year, month, date |
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 ], |
279 | ); |
280 | |
281 | |
282 | while( my($ical_str, $expect) = each %ICal_Dates ) { |
283 | my $ical = Date::ICal->new( ical => $ical_str ); |
284 | |
285 | ok( defined $ical, "new(ical => '$ical_str')" ); |
286 | ok( $ical->isa('Date::ICal'), " and it's the right class" ); |
287 | |
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()' ); |
294 | } |
295 | |
296 | So now we can test bunches of dates by just adding them to |
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297 | C<%ICal_Dates>. Now that it's less work to test with more dates, you'll |
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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 |
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300 | the C<use Test::More tests =E<gt> ##> line. That can rapidly get |
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301 | annoying. There's two ways to make this work better. |
302 | |
303 | First, we can calculate the plan dynamically using the C<plan()> |
304 | function. |
305 | |
306 | use Test::More; |
307 | use Date::ICal; |
308 | |
309 | my %ICal_Dates = ( |
310 | ...same as before... |
311 | ); |
312 | |
313 | # For each key in the hash we're running 8 tests. |
314 | plan tests => keys %ICal_Dates * 8; |
315 | |
316 | Or to be even more flexible, we use C<no_plan>. This means we're just |
317 | running some tests, don't know how many. [6] |
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318 | |
319 | use Test::More 'no_plan'; # instead of tests => 32 |
320 | |
321 | now we can just add tests and not have to do all sorts of math to |
322 | figure out how many we're running. |
323 | |
324 | |
325 | =head2 Informative names |
326 | |
327 | Take a look at this line here |
328 | |
329 | ok( defined $ical, "new(ical => '$ical_str')" ); |
330 | |
331 | we've added more detail about what we're testing and the ICal string |
332 | itself we're trying out to the name. So you get results like: |
333 | |
334 | ok 25 - new(ical => '19971024T120000') |
335 | ok 26 - and it's the right class |
336 | ok 27 - year() |
337 | ok 28 - month() |
338 | ok 29 - day() |
339 | ok 30 - hour() |
340 | ok 31 - min() |
341 | ok 32 - sec() |
342 | |
343 | if something in there fails, you'll know which one it was and that |
344 | will make tracking down the problem easier. So try to put a bit of |
345 | debugging information into the test names. |
346 | |
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347 | Describe what the tests test, to make debugging a failed test easier |
348 | for you or for the next person who runs your test. |
349 | |
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350 | |
351 | =head2 Skipping tests |
352 | |
353 | Poking around in the existing Date::ICal tests, I found this in |
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354 | F<t/01sanity.t> [7] |
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355 | |
356 | #!/usr/bin/perl -w |
357 | |
358 | use Test::More tests => 7; |
359 | use Date::ICal; |
360 | |
361 | # Make sure epoch time is being handled sanely. |
362 | my $t1 = Date::ICal->new( epoch => 0 ); |
363 | is( $t1->epoch, 0, "Epoch time of 0" ); |
364 | |
365 | # XXX This will only work on unix systems. |
366 | is( $t1->ical, '19700101Z', " epoch to ical" ); |
367 | |
368 | is( $t1->year, 1970, " year()" ); |
369 | is( $t1->month, 1, " month()" ); |
370 | is( $t1->day, 1, " day()" ); |
371 | |
372 | # like the tests above, but starting with ical instead of epoch |
373 | my $t2 = Date::ICal->new( ical => '19700101Z' ); |
374 | is( $t2->ical, '19700101Z', "Start of epoch in ICal notation" ); |
375 | |
376 | is( $t2->epoch, 0, " and back to ICal" ); |
377 | |
378 | The beginning of the epoch is different on most non-Unix operating |
379 | systems [8]. Even though Perl smooths out the differences for the most |
380 | part, certain ports do it differently. MacPerl is one off the top of |
381 | my head. [9] We I<know> this will never work on MacOS. So rather than |
382 | just putting a comment in the test, we can explicitly say it's never |
383 | going to work and skip the test. |
384 | |
385 | use Test::More tests => 7; |
386 | use Date::ICal; |
387 | |
388 | # Make sure epoch time is being handled sanely. |
389 | my $t1 = Date::ICal->new( epoch => 0 ); |
390 | is( $t1->epoch, 0, "Epoch time of 0" ); |
391 | |
392 | SKIP: { |
393 | skip('epoch to ICal not working on MacOS', 6) |
394 | if $^O eq 'MacOS'; |
395 | |
396 | is( $t1->ical, '19700101Z', " epoch to ical" ); |
397 | |
398 | is( $t1->year, 1970, " year()" ); |
399 | is( $t1->month, 1, " month()" ); |
400 | is( $t1->day, 1, " day()" ); |
401 | |
402 | # like the tests above, but starting with ical instead of epoch |
403 | my $t2 = Date::ICal->new( ical => '19700101Z' ); |
404 | is( $t2->ical, '19700101Z', "Start of epoch in ICal notation" ); |
405 | |
406 | is( $t2->epoch, 0, " and back to ICal" ); |
407 | } |
408 | |
409 | A little bit of magic happens here. When running on anything but |
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410 | MacOS, all the tests run normally. But when on MacOS, C<skip()> causes |
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411 | the entire contents of the SKIP block to be jumped over. It's never |
412 | run. Instead, it prints special output that tells Test::Harness that |
413 | the tests have been skipped. |
414 | |
415 | 1..7 |
416 | ok 1 - Epoch time of 0 |
417 | ok 2 # skip epoch to ICal not working on MacOS |
418 | ok 3 # skip epoch to ICal not working on MacOS |
419 | ok 4 # skip epoch to ICal not working on MacOS |
420 | ok 5 # skip epoch to ICal not working on MacOS |
421 | ok 6 # skip epoch to ICal not working on MacOS |
422 | ok 7 # skip epoch to ICal not working on MacOS |
423 | |
424 | This means your tests won't fail on MacOS. This means less emails |
425 | from MacPerl users telling you about failing tests that you know will |
426 | never work. You've got to be careful with skip tests. These are for |
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427 | tests which don't work and I<never will>. It is not for skipping |
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428 | genuine bugs (we'll get to that in a moment). |
429 | |
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430 | The tests are wholly and completely skipped. [10] This will work. |
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431 | |
432 | SKIP: { |
433 | skip("I don't wanna die!"); |
434 | |
435 | die, die, die, die, die; |
436 | } |
437 | |
438 | |
439 | =head2 Todo tests |
440 | |
441 | Thumbing through the Date::ICal man page, I came across this: |
442 | |
443 | ical |
444 | |
445 | $ical_string = $ical->ical; |
446 | |
447 | Retrieves, or sets, the date on the object, using any |
448 | valid ICal date/time string. |
449 | |
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450 | "Retrieves or sets". Hmmm, didn't see a test for using C<ical()> to set |
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451 | the date in the Date::ICal test suite. So I'll write one. |
452 | |
453 | use Test::More tests => 1; |
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454 | use Date::ICal; |
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455 | |
456 | my $ical = Date::ICal->new; |
457 | $ical->ical('20201231Z'); |
458 | is( $ical->ical, '20201231Z', 'Setting via ical()' ); |
459 | |
460 | run that and I get |
461 | |
462 | 1..1 |
463 | not ok 1 - Setting via ical() |
464 | # Failed test (- at line 6) |
465 | # got: '20010814T233649Z' |
466 | # expected: '20201231Z' |
467 | # Looks like you failed 1 tests of 1. |
468 | |
469 | Whoops! Looks like it's unimplemented. Let's assume we don't have |
470 | the time to fix this. [11] Normally, you'd just comment out the test |
471 | and put a note in a todo list somewhere. Instead, we're going to |
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472 | explicitly state "this test will fail" by wrapping it in a C<TODO> block. |
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473 | |
474 | use Test::More tests => 1; |
475 | |
476 | TODO: { |
477 | local $TODO = 'ical($ical) not yet implemented'; |
478 | |
479 | my $ical = Date::ICal->new; |
480 | $ical->ical('20201231Z'); |
481 | |
482 | is( $ical->ical, '20201231Z', 'Setting via ical()' ); |
483 | } |
484 | |
485 | Now when you run, it's a little different: |
486 | |
487 | 1..1 |
488 | not ok 1 - Setting via ical() # TODO ical($ical) not yet implemented |
489 | # got: '20010822T201551Z' |
490 | # expected: '20201231Z' |
491 | |
492 | Test::More doesn't say "Looks like you failed 1 tests of 1". That '# |
493 | TODO' tells Test::Harness "this is supposed to fail" and it treats a |
494 | failure as a successful test. So you can write tests even before |
495 | you've fixed the underlying code. |
496 | |
497 | If a TODO test passes, Test::Harness will report it "UNEXPECTEDLY |
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498 | SUCCEEDED". When that happens, you simply remove the TODO block with |
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499 | C<local $TODO> and turn it into a real test. |
500 | |
501 | |
502 | =head2 Testing with taint mode. |
503 | |
504 | Taint mode is a funny thing. It's the globalest of all global |
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505 | features. Once you turn it on, it affects I<all> code in your program |
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506 | and I<all> modules used (and all the modules they use). If a single |
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507 | piece of code isn't taint clean, the whole thing explodes. With that |
508 | in mind, it's very important to ensure your module works under taint |
509 | mode. |
510 | |
511 | It's very simple to have your tests run under taint mode. Just throw |
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512 | a C<-T> into the C<#!> line. Test::Harness will read the switches |
513 | in C<#!> and use them to run your tests. |
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514 | |
515 | #!/usr/bin/perl -Tw |
516 | |
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517 | ...test normally here... |
518 | |
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519 | So when you say C<make test> it will be run with taint mode and |
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520 | warnings on. |
521 | |
522 | |
523 | =head1 FOOTNOTES |
524 | |
525 | =over 4 |
526 | |
527 | =item 1 |
528 | |
529 | The first number doesn't really mean anything, but it has to be 1. |
530 | It's the second number that's important. |
531 | |
532 | =item 2 |
533 | |
534 | For those following along at home, I'm using version 1.31. It has |
535 | some bugs, which is good -- we'll uncover them with our tests. |
536 | |
537 | =item 3 |
538 | |
539 | You can actually take this one step further and test the manual |
4bd4e70a |
540 | itself. Have a look at B<Test::Inline> (formerly B<Pod::Tests>). |
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541 | |
542 | =item 4 |
543 | |
544 | Yes, there's a mistake in the test suite. What! Me, contrived? |
545 | |
546 | =item 5 |
547 | |
548 | We'll get to testing the contents of lists later. |
549 | |
550 | =item 6 |
551 | |
552 | But what happens if your test program dies halfway through?! Since we |
553 | didn't say how many tests we're going to run, how can we know it |
554 | failed? No problem, Test::More employs some magic to catch that death |
555 | and turn the test into a failure, even if every test passed up to that |
556 | point. |
557 | |
558 | =item 7 |
559 | |
560 | I cleaned it up a little. |
561 | |
562 | =item 8 |
563 | |
564 | Most Operating Systems record time as the number of seconds since a |
565 | certain date. This date is the beginning of the epoch. Unix's starts |
566 | at midnight January 1st, 1970 GMT. |
567 | |
568 | =item 9 |
569 | |
570 | MacOS's epoch is midnight January 1st, 1904. VMS's is midnight, |
571 | November 17th, 1858, but vmsperl emulates the Unix epoch so it's not a |
572 | problem. |
573 | |
574 | =item 10 |
575 | |
576 | As long as the code inside the SKIP block at least compiles. Please |
577 | don't ask how. No, it's not a filter. |
578 | |
579 | =item 11 |
580 | |
581 | Do NOT be tempted to use TODO tests as a way to avoid fixing simple |
582 | bugs! |
583 | |
584 | =back |
4bd4e70a |
585 | |
586 | =head1 AUTHORS |
587 | |
588 | Michael G Schwern E<lt>schwern@pobox.comE<gt> and the perl-qa dancers! |
589 | |
590 | =head1 COPYRIGHT |
591 | |
592 | Copyright 2001 by Michael G Schwern E<lt>schwern@pobox.comE<gt>. |
593 | |
594 | This documentation is free; you can redistribute it and/or modify it |
595 | under the same terms as Perl itself. |
596 | |
597 | Irrespective of its distribution, all code examples in these files |
598 | are hereby placed into the public domain. You are permitted and |
599 | encouraged to use this code in your own programs for fun |
600 | or for profit as you see fit. A simple comment in the code giving |
601 | credit would be courteous but is not required. |
602 | |
603 | =cut |