tutorial(3)

NAME

Test::Tutorial - A tutorial about writing really basic
tests

DESCRIPTION

AHHHHHHH!!!! NOT TESTING! Anything but testing! Beat me, whip me, send me to Detroit, but don't make me write tests!

*sob*

Besides, I don't know how to write the damned things.

Is this you? Is writing tests right up there with writing documentation and having your fingernails pulled out? Did you open up a test and read: ######## We start with some black magic
and decide that's quite enough for you?
It's ok. That's all gone now. We've done all the black magic for you. And here are the tricks...
Nuts and bolts of testing.
Here's the most basic test program.: #!/usr/bin/perl -w; print "1..10;; print 1 + 1 == 2 ? "ok 10 : "not ok 10;
since 1 + 1 is 2, it prints:: 1..1
ok 1
What this says is: 1..1 "I'm going to run one test." [1]
"ok 1" "The first test passed". And that's about all
magic there is to testing. Your basic unit of testing is
the ok. For each thing you test, an "ok" is printed.
Simple. Test::Harness interprets your test results to determine if you succeeded or failed (more on that later).
Writing all these print statements rapidly gets tedious.
Fortunately, there's Test::Simple. It has one function, "ok()".: #!/usr/bin/perl -w; use Test::Simple tests => 1;; ok( 1 + 1 == 2 );
and that does the same thing as the code above. "ok()" is the backbone of Perl testing, and we'll be using it instead of roll-your-own from here on. If "ok()" gets a true value, the test passes. False, it fails.: #!/usr/bin/perl -w; use Test::Simple tests => 2;
ok( 1 + 1 == 2 );
ok( 2 + 2 == 5 );
from that comes: 1..2
ok 1
not ok 2
# Failed test (test.pl at line 5)
# Looks like you failed 1 tests of 2.
1..2 "I'm going to run two tests." This number is used to ensure your test program ran all the way through and didn't die or skip some tests. "ok 1" "The first test passed." "not ok 2" "The second test failed". Test::Sim ple helpfully prints out some extra commentary about your tests.
It's not scary. Come, hold my hand. We're going to give
an example of testing a module. For our example, we'll be
testing a date library, Date::ICal. It's on CPAN, so download a copy and follow along. [2]
Where to start?
This is the hardest part of testing, where do you start? People often get overwhelmed at the apparent enormity of the task of testing a whole module. Best place to start is at the beginning. Date::ICal is an object-oriented module, and that means you start by making an object. So we test "new()".: #!/usr/bin/perl -w; use Test::Simple tests => 2;; use Date::ICal;; my $ical = Date::ICal->new; # create an object
ok( defined $ical ); # check that we; got something
ok( $ical->isa('Date::ICal') ); # and it's the; right class
run that and you should get:: 1..2
ok 1
ok 2
congratulations, you've written your first useful test.
Names
That output isn't terribly descriptive, is it? When you have two tests you can figure out which one is #2, but what if you have 102?
Each test can be given a little descriptive name as the second argument to "ok()".: use Test::Simple tests => 2;; ok( defined $ical, 'new() returned some; thing' );
ok( $ical->isa('Date::ICal'), " and it's the right; class" );
So now you'd see...: 1..2
ok 1 - new() returned something
ok 2 - and it's the right class
Test the manual
Simplest way to build up a decent testing suite is to just test what the manual says it does. [3] Let's pull some thing out of the "SYNOPSIS" in Date::ICal and test that all its bits work.: #!/usr/bin/perl -w; use Test::Simple tests => 8;; use Date::ICal;; $ical = Date::ICal->new( year => 1964, month => 10,; day => 16,
hour => 16, min => 12, sec =>

47,
tz => '0530' );
ok( defined $ical, 'new() returned some
thing' ); ok( $ical->isa('Date::ICal'), " and it's the right
class" ); ok( $ical->sec == 47, ' sec()' ); ok( $ical->min == 12, ' min()' ); ok( $ical->hour == 16, ' hour()' ); ok( $ical->day == 17, ' day()' ); ok( $ical->month == 10, ' month()' ); ok( $ical->year == 1964, ' year()' );
run that and you get:: 1..8
ok 1 - new() returned something
ok 2 - and it's the right class
ok 3 - sec()
ok 4 - min()
ok 5 - hour()
not ok 6 - day()
# Failed test (- at line 16)
ok 7 - month()
ok 8 - year()
# Looks like you failed 1 tests of 8.
Whoops, a failure! [4] Test::Simple helpfully lets us know on what line the failure occured, but not much else. We were supposed to get 17, but we didn't. What did we get?? Dunno. We'll have to re-run the test in the debugger or throw in some print statements to find out.
Instead, we'll switch from Test::Simple to Test::More. Test::More does everything Test::Simple does, and more! In fact, Test::More does things exactly the way Test::Sim ple does. You can literally swap Test::Simple out and put
Test::More in its place. That's just what we're going to
do.
Test::More does more than Test::Simple. The most impor tant difference at this point is it provides more informa tive ways to say "ok". Although you can write almost any test with a generic "ok()", it can't tell you what went wrong. Instead, we'll use the "is()" function, which lets us declare that something is supposed to be the same as something else:: #!/usr/bin/perl -w; use Test::More tests => 8;; use Date::ICal;; $ical = Date::ICal->new( year => 1964, month => 10,; day => 16,
hour => 16, min => 12, sec =>

47,
tz => '0530' );
ok( defined $ical, 'new() returned some
thing' ); ok( $ical->isa('Date::ICal'), " and it's the right
class" ); is( $ical->sec, 47, ' sec()' ); is( $ical->min, 12, ' min()' ); is( $ical->hour, 16, ' hour()' ); is( $ical->day, 17, ' day()' ); is( $ical->month, 10, ' month()' ); is( $ical->year, 1964, ' year()' );
"Is "$ical->sec" 47?" "Is "$ical->min" 12?" With "is()" in place, you get some more information: 1..8
ok 1 - new() returned something
ok 2 - and it's the right class
ok 3 - sec()
ok 4 - min()
ok 5 - hour()
not ok 6 - day()
# Failed test (- at line 16)
# got: '16'
# expected: '17'
ok 7 - month()
ok 8 - year()
# Looks like you failed 1 tests of 8.
letting us know that "$ical->day" returned 16, but we expected 17. A quick check shows that the code is working fine, we made a mistake when writing up the tests. Just change it to:: is( $ical->day, 16, ' day()' );
and everything works.
So any time you're doing a "this equals that" sort of test, use "is()". It even works on arrays. The test is always in scalar context, so you can test how many ele ments are in a list this way. [5]: is( @foo, 5, 'foo has 5 elements' );
Sometimes the tests are wrong
Which brings us to a very important lesson. Code has bugs. Tests are code. Ergo, tests have bugs. A failing test could mean a bug in the code, but don't discount the possibility that the test is wrong.
On the flip side, don't be tempted to prematurely declare a test incorrect just because you're having trouble find ing the bug. Invalidating a test isn't something to be taken lightly, and don't use it as a cop out to avoid work.
Testing lots of values
We're going to be wanting to test a lot of dates here, trying to trick the code with lots of different edge cases. Does it work before 1970? After 2038? Before 1904? Do years after 10,000 give it trouble? Does it get leap years right? We could keep repeating the code above, or we could set up a little try/expect loop.: use Test::More tests => 32;
use Date::ICal;; my %ICal_Dates = (
# An ICal string And the year, month, date
# hour, minute and second

we expect.
'19971024T120000' => # from the docs.
[ 1997, 10, 24, 12, 0, 0

],

'20390123T232832' => # after the Unix epoch

[ 2039, 1, 23, 23, 28, 32

],

'19671225T000000' => # before the Unix

epoch

[ 1967, 12, 25, 0, 0, 0

],

'18990505T232323' => # before the MacOS

epoch

[ 1899, 5, 5, 23, 23, 23

],

);

while( my($ical_str, $expect) = each %ICal_Dates ) {

my $ical = Date::ICal->new( ical => $ical_str );

ok( defined $ical, "new(ical =>

'$ical_str')" );
ok( $ical->isa('Date::ICal'), " and it's the

right class" );

is( $ical->year, $expect->[0], ' year()'

);
is( $ical->month, $expect->[1], ' month()'

);
is( $ical->day, $expect->[2], ' day()'

);
is( $ical->hour, $expect->[3], ' hour()'

);
is( $ical->min, $expect->[4], ' min()'

);
is( $ical->sec, $expect->[5], ' sec()'

);

}; So now we can test bunches of dates by just adding them to
%ICal_Dates. Now that it's less work to test with more
dates, you'll be inclined to just throw more in as you
think of them. Only problem is, every time we add to that
we have to keep adjusting the "use Test::More tests => ##"
line. That can rapidly get annoying. Instead we use
"no_plan". This means we're just running some tests,
don't know how many. [6]

use Test::More 'no_plan'; # instead of tests => 32; now we can just add tests and not have to do all sorts of
math to figure out how many we're running.; Informative names; Take a look at this line here

ok( defined $ical, "new(ical =>

'$ical_str')" );; we've added more detail about what we're testing and the
ICal string itself we're trying out to the name. So you
get results like:

ok 25 - new(ical => '19971024T120000')
ok 26 - and it's the right class
ok 27 - year()
ok 28 - month()
ok 29 - day()
ok 30 - hour()
ok 31 - min()
ok 32 - sec(); if something in there fails, you'll know which one it was
and that will make tracking down the problem easier. So
try to put a bit of debugging information into the test
names.; Describe what the tests test, to make debugging a failed
test easier for you or for the next person who runs your
test.; Skipping tests; Poking around in the existing Date::ICal tests, I found
this in t/01sanity.t [7]

#!/usr/bin/perl -w

use Test::More tests => 7;
use Date::ICal;

# Make sure epoch time is being handled sanely.
my $t1 = Date::ICal->new( epoch => 0 );
is( $t1->epoch, 0, "Epoch time of 0" );

# XXX This will only work on unix systems.
is( $t1->ical, '19700101Z', " epoch to ical" );

is( $t1->year, 1970, " year()" );
is( $t1->month, 1, " month()" );
is( $t1->day, 1, " day()" );

# like the tests above, but starting with ical instead

of epoch
my $t2 = Date::ICal->new( ical => '19700101Z' );
is( $t2->ical, '19700101Z', "Start of epoch in ICal

notation" );

is( $t2->epoch, 0, " and back to ICal" );; The beginning of the epoch is different on most non-Unix
operating systems [8]. Even though Perl smooths out the
differences for the most part, certain ports do it differ
ently. MacPerl is one off the top of my head. [9] We know
this will never work on MacOS. So rather than just
putting a comment in the test, we can explicitly say it's
never going to work and skip the test.

use Test::More tests => 7;
use Date::ICal;

# Make sure epoch time is being handled sanely.
my $t1 = Date::ICal->new( epoch => 0 );
is( $t1->epoch, 0, "Epoch time of 0" );

SKIP: {
skip('epoch to ICal not working on MacOS', 6)
if $^O eq 'MacOS';

is( $t1->ical, '19700101Z', " epoch to ical" );

is( $t1->year, 1970, " year()" );
is( $t1->month, 1, " month()" );
is( $t1->day, 1, " day()" );

# like the tests above, but starting with ical in

stead of epoch
my $t2 = Date::ICal->new( ical => '19700101Z' );
is( $t2->ical, '19700101Z', "Start of epoch in

ICal notation" );

is( $t2->epoch, 0, " and back to ICal"

);

}; A little bit of magic happens here. When running on any
thing but MacOS, all the tests run normally. But when on
MacOS, "skip()" causes the entire contents of the SKIP
block to be jumped over. It's never run. Instead, it
prints special output that tells Test::Harness that the
tests have been skipped.

1..7
ok 1 - Epoch time of 0
ok 2 # skip epoch to ICal not working on MacOS
ok 3 # skip epoch to ICal not working on MacOS
ok 4 # skip epoch to ICal not working on MacOS
ok 5 # skip epoch to ICal not working on MacOS
ok 6 # skip epoch to ICal not working on MacOS
ok 7 # skip epoch to ICal not working on MacOS; This means your tests won't fail on MacOS. This means
less emails from MacPerl users telling you about failing
tests that you know will never work. You've got to be
careful with skip tests. These are for tests which don't
work and never will. It is not for skipping genuine bugs (we'll get to that in a moment).; The tests are wholly and completely skipped. [10] This
will work.

SKIP: {
skip("I don't wanna die!");

die, die, die, die, die;

}; Todo tests; Thumbing through the Date::ICal man page, I came across
this:

ical

$ical_string = $ical->ical;

Retrieves, or sets, the date on the object, using any
valid ICal date/time string.; "Retrieves or sets". Hmmm, didn't see a test for using
"ical()" to set the date in the Date::ICal test suite. So
I'll write one.

use Test::More tests => 1;
use Date::ICal;

my $ical = Date::ICal->new;
$ical->ical('20201231Z');
is( $ical->ical, '20201231Z', 'Setting via ical()'

);; run that and I get

1..1
not ok 1 - Setting via ical()
# Failed test (- at line 6)
# got: '20010814T233649Z'
# expected: '20201231Z'
# Looks like you failed 1 tests of 1.; Whoops! Looks like it's unimplemented. Let's assume we
don't have the time to fix this. [11] Normally, you'd just
comment out the test and put a note in a todo list some
where. Instead, we're going to explicitly state "this
test will fail" by wrapping it in a "TODO" block.

use Test::More tests => 1;

TODO: {
local $TODO = 'ical($ical) not yet implemented';

my $ical = Date::ICal->new;
$ical->ical('20201231Z');

is( $ical->ical, '20201231Z', 'Setting via

ical()' );

}; Now when you run, it's a little different:

1..1
not ok 1 - Setting via ical() # TODO ical($ical) not

yet implemented
# got: '20010822T201551Z'
# expected: '20201231Z'; Test::More doesn't say "Looks like you failed 1 tests of
1". That '# TODO' tells Test::Harness "this is supposed
to fail" and it treats a failure as a successful test. So
you can write tests even before you've fixed the underly
ing code.; If a TODO test passes, Test::Harness will report it "UNEX
PECTEDLY SUCCEEDED". When that happens, you simply remove
the TODO block with "local $TODO" and turn it into a real
test.; Testing with taint mode.; Taint mode is a funny thing. It's the globalest of all
global features. Once you turn it on it effects all code
in your program and all modules used (and all the modules
they use). If a single piece of code isn't taint clean,
the whole thing explodes. With that in mind, it's very
important to ensure your module works under taint mode.; It's very simple to have your tests run under taint mode.
Just throw a "-T" into the "#!" line. Test::Harness will
read the switches in "#!" and use them to run your tests.

#!/usr/bin/perl -Tw

use Test::More 'no_plan';

...test normally here...; So when you say "make test" it will be run with taint mode
and warnings on.

FOOTNOTES

1 The first number doesn't really mean anything, but it: has to be 1. It's the second number that's important.
2 For those following along at home, I'm using version: 1.31. It has some bugs, which is good -- we'll
uncover them with our tests.
3 You can actually take this one step further and test: the manual itself. Have a look at Test::Inline (for merly Pod::Tests).
4 Yes, there's a mistake in the test suite. What! Me,: contrived?
5 We'll get to testing the contents of lists later.
6 But what happens if your test program dies halfway: through?! Since we didn't say how many tests we're
going to run, how can we know it failed? No problem,
Test::More employs some magic to catch that death and
turn the test into a failure, even if every test
passed up to that point.
7 I cleaned it up a little.
8 Most Operating Systems record time as the number of: seconds since a certain date. This date is the begin
ning of the epoch. Unix's starts at midnight January
1st, 1970 GMT.
9 MacOS's epoch is midnight January 1st, 1904. VMS's is: midnight, November 17th, 1858, but vmsperl emulates
the Unix epoch so it's not a problem.
10 As long as the code inside the SKIP block at least: compiles. Please don't ask how. No, it's not a fil
ter.
11 Do NOT be tempted to use TODO tests as a way to avoid: fixing simple bugs!

AUTHORS

Michael G Schwern <schwern@pobox.com> and the perl-qa
dancers!

COPYRIGHT

This documentation is free; you can redistribute it and/or
modify it under the same terms as Perl itself.

Irrespective of its distribution, all code examples in
these files are hereby placed into the public domain. You
are permitted and encouraged to use this code in your own
programs for fun or for profit as you see fit. A simple
comment in the code giving credit would be courteous but
is not required.

docs.sk