I'm writing up a Test::Tutorial and a Test::FAQ to go along with
Test::Simple. I've attached a vestigal Test::Tutorial so you can see
where it's going (I'm literally in the middle of writing it, so yes,
it's incomplete) and comment on the overall style.
For Test::FAQ, I need FAQs and answers. So far I've got:
Are there any modules for testing?
I'll just point them at Test::Simple
Are there any modules for testing web pages/CGI programs?
I know there's a few out there, CGI::Test, WWW::Chat... but I've never
used them. Anyone?
Are there any modules for testing external programs?
Test::Cmd exists, but I don't know much about it.
Are there any mailing lists for testing?
[EMAIL PROTECTED], [EMAIL PROTECTED]
Can you do XUnit/JUnit style testing in Perl?
Point them at Pod::Tests with a mention of Test::Unit (unfortunately,
not ready for prime-time).
How do I test my module is backwards/forwards compatible?
I outline that Makefile.PL/test_via_harness() override trick.
More questions, preferably with answers, wanted (doesn't have to be
perfect, I can flesh it out.)
--
Michael G. Schwern <[EMAIL PROTECTED]> http://www.pobox.com/~schwern/
Perl6 Quality Assurance <[EMAIL PROTECTED]> Kwalitee Is Job One
Monkey tennis
=head1 NAME
Test::Tutorial - A tutorial about writing really basic tests
=head1 DESCRIPTION
AHHHHHHH!!!! NOT B<TESTING>! Anything but testing!
Beat me, whip me, send me to I<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?
=head2 Nuts and bolts of testing.
Here's the most basic test program.
#!/usr/bin/perl -w
print "1..1\n";
print (1 + 1 == 2) ? "ok 1\n" : "not ok 1\n";
since 1 + 1 is 2, it prints:
1..1
ok 1
What this says is: C<1..1> "I'm going to run one test." C<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.
C<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. C<ok 1> "The first test passed." C<not ok 2> "The second test
failed". Test::Simple helpfuly 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. []
=head2 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.
=head2 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().
ok( defined $ical, 'new() returned something' );
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
=head2 Test the manual
Simplest way to build up a decent testing suite is to just test what
the manual says it does. [] Let's pull something out of of the
Date::ICal SYNOPSIS and test that all it's 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 something' );
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! [] 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 I<exactly> the way Test::Simple does. You can literally swap
Test::Simple out and put Test::More in it's place. That's just what
we're going to do.
Test::More provides more informative ways to say 'ok'. ok() is nice
and generic, you can write almost any test with it, but it can't tell
you what went wrong. For that, we use the is() function.
#!/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 something' );
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 make a mistake
when writing up the tests. Just change it to:
is( $ical->day, 16, ' day()' );
and everything works.
So any time you're doing a "this equals that" sort of test, use is().
It even works on arrays. The test is always in scalar context, so you
can test how many elements are in a list this way. []
is( @foo, 5, 'foo has 5 elements' );
=head2 Sometimes the tests are wrong
Which brings us to a very important lesson. Code has bugs. Tests are
code. Ergo, tests have bugs. A failing test could mean a bug in the
code, but don't discount the possibility that the test is wrong.
On the flip side, don't be tempted to prematurely declare a test
incorrect just because you're having trouble finding the bug.
Invalidating a test isn't something to be taken lightly, and don't use
it as a cop out to avoid work.
=head2 Testing lots of values
We're going to be wanting to test a lot of dates here, trying to trick
the code with lots of different edge cases. Does it work before 1970?
After 2038? Before 1904? Do years after 10,000 give it trouble?
Does it get leap years right? We could keep repeating the code above,
or we could set up a little try/expect loop.
use Test::More tests => 32;
use Date::ICal;
my %ICal_Dates = (
# An ICal string And the year, month, date
# hour, minute and second we expect.
'19971024T120000' => # from the docs.
[ 1997, 10, 24, 12, 0, 0 ],
'20390123T232832' => # after the Unix epoch
[ 2039, 1, 23, 23, 28, 32 ],
'19671225T000000' => # before the Unix epoch
[ 1967, 12, 25, 0, 0, 0 ],
'18990505T232323' => # before the MacOS epoch
[ 1899, 5, 5, 23, 23, 23 ],
);
while( my($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 C<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. []
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.
=head2 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.
=head2 Skipping tests
Poking around in the existing Date::ICal tests, I found this in
t/01sanity.t []
#!/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 []. Even though Perl smooths out the differences for the most
part, certain ports do it differently. MacPerl is one off the top of
my head. [] We I<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.
# 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 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" );
}
A little bit of magic happens here. When running on anything 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 B<never will>. It is not for skipping
genuine bugs (we'll get to that in a moment).
The tests are wholely and completely skipped. [] This will work.
SKIP: {
skip("I don't wanna die!");
die, die, die, die, die;
}
=head2 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.
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!
=head1 FOOTNOTES
=over 4
=item
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.
=item
You can actually take this one step further and test the manual
itself. Have a look at Pod::Tests (soon to be Test::Inline).
=item
Yes, there's a mistake in the test suite. What! Me, contrived?
=item
We'll get to testing the contents of lists later.
=item
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.
=item
I cleaned it up a little.
=item
XXX what's an epoch
=item
mumble 1904
=item
As long as the code inside the SKIP block at least compiles. Please
don't ask how. No, it's not a filter.
=back
