Test(3p) Perl Programmers Reference Guide Test(3p)
Test - provides a simple framework for writing test scripts
use strict;
use Test;
# use a BEGIN block so we print our plan before MyModule is loaded
BEGIN { plan tests => 14, todo => [3,4] }
# load your module...
use MyModule;
# Helpful notes. All note-lines must start with a "#".
print "# I'm testing MyModule version $MyModule::VERSION\n";
ok(0); # failure
ok(1); # success
ok(0); # ok, expected failure (see todo list, above)
ok(1); # surprise success!
ok(0,1); # failure: '0' ne '1'
ok('broke','fixed'); # failure: 'broke' ne 'fixed'
ok('fixed','fixed'); # success: 'fixed' eq 'fixed'
ok('fixed',qr/x/); # success: 'fixed' =~ qr/x/
ok(sub { 1+1 }, 2); # success: '2' eq '2'
ok(sub { 1+1 }, 3); # failure: '2' ne '3'
my @list = (0,0);
ok @list, 3, "\@list=".join(',',@list); #extra notes
ok 'segmentation fault', '/(?i)success/'; #regex match
skip(
$^O =~ m/MSWin/ ? "Skip if MSWin" : 0, # whether to skip
$foo, $bar # arguments just like for ok(...)
);
skip(
$^O =~ m/MSWin/ ? 0 : "Skip unless MSWin", # whether to skip
$foo, $bar # arguments just like for ok(...)
);
This module simplifies the task of writing test files for
Perl modules, such that their output is in the format that
Test::Harness expects to see.
To write a test for your new (and probably not even done)
module, create a new file called t/test.t (in a new t direc-
tory). If you have multiple test files, to test the "foo",
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"bar", and "baz" feature sets, then feel free to call your
files t/foo.t, t/bar.t, and t/baz.t
Functions
This module defines three public functions, "plan(...)",
"ok(...)", and "skip(...)". By default, all three are
exported by the "use Test;" statement.
"plan(...)"
BEGIN { plan %theplan; }
This should be the first thing you call in your test
script. It declares your testing plan, how many there
will be, if any of them should be allowed to fail, and
so on.
Typical usage is just:
use Test;
BEGIN { plan tests => 23 }
These are the things that you can put in the parameters
to plan:
"tests => number"
The number of tests in your script. This means all
ok() and skip() calls.
"todo => [1,5,14]"
A reference to a list of tests which are allowed to
fail. See "TODO TESTS".
"onfail => sub { ... }"
"onfail => \&some_sub"
A subroutine reference to be run at the end of the
test script, if any of the tests fail. See
"ONFAIL".
You must call "plan(...)" once and only once. You
should call it in a "BEGIN {...}" block, like so:
BEGIN { plan tests => 23 }
"ok(...)"
ok(1 + 1 == 2);
ok($have, $expect);
ok($have, $expect, $diagnostics);
This function is the reason for "Test"'s existence.
It's the basic function that handles printing ""ok"" or
""not ok"", along with the current test number. (That's
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what "Test::Harness" wants to see.)
In its most basic usage, "ok(...)" simply takes a single
scalar expression. If its value is true, the test
passes; if false, the test fails. Examples:
# Examples of ok(scalar)
ok( 1 + 1 == 2 ); # ok if 1 + 1 == 2
ok( $foo =~ /bar/ ); # ok if $foo contains 'bar'
ok( baz($x + $y) eq 'Armondo' ); # ok if baz($x + $y) returns
# 'Armondo'
ok( @a == @b ); # ok if @a and @b are the same length
The expression is evaluated in scalar context. So the
following will work:
ok( @stuff ); # ok if @stuff has any elements
ok( !grep !defined $_, @stuff ); # ok if everything in @stuff is
# defined.
A special case is if the expression is a subroutine
reference (in either "sub {...}" syntax or "\&foo" syn-
tax). In that case, it is executed and its value (true
or false) determines if the test passes or fails. For
example,
ok( sub { # See whether sleep works at least passably
my $start_time = time;
sleep 5;
time() - $start_time >= 4
});
In its two-argument form, "ok(arg1, arg2)" compares the
two scalar values to see if they match. They match if
both are undefined, or if arg2 is a regex that matches
arg1, or if they compare equal with "eq".
# Example of ok(scalar, scalar)
ok( "this", "that" ); # not ok, 'this' ne 'that'
ok( "", undef ); # not ok, "" is defined
The second argument is considered a regex if it is
either a regex object or a string that looks like a
regex. Regex objects are constructed with the qr//
operator in recent versions of perl. A string is con-
sidered to look like a regex if its first and last char-
acters are "/", or if the first character is "m" and its
second and last characters are both the same non-
alphanumeric non-whitespace character. These regexp
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Regex examples:
ok( 'JaffO', '/Jaff/' ); # ok, 'JaffO' =~ /Jaff/
ok( 'JaffO', 'm|Jaff|' ); # ok, 'JaffO' =~ m|Jaff|
ok( 'JaffO', qr/Jaff/ ); # ok, 'JaffO' =~ qr/Jaff/;
ok( 'JaffO', '/(?i)jaff/ ); # ok, 'JaffO' =~ /jaff/i;
If either (or both!) is a subroutine reference, it is
run and used as the value for comparing. For example:
ok sub {
open(OUT, ">x.dat") || die $!;
print OUT "\x{e000}";
close OUT;
my $bytecount = -s 'x.dat';
unlink 'x.dat' or warn "Can't unlink : $!";
return $bytecount;
},
4
;
The above test passes two values to "ok(arg1, arg2)" --
the first a coderef, and the second is the number 4.
Before "ok" compares them, it calls the coderef, and
uses its return value as the real value of this parame-
ter. Assuming that $bytecount returns 4, "ok" ends up
testing "4 eq 4". Since that's true, this test passes.
Finally, you can append an optional third argument, in
"ok(arg1,arg2, note)", where note is a string value that
will be printed if the test fails. This should be some
useful information about the test, pertaining to why it
failed, and/or a description of the test. For example:
ok( grep($_ eq 'something unique', @stuff), 1,
"Something that should be unique isn't!\n".
'@stuff = '.join ', ', @stuff
);
Unfortunately, a note cannot be used with the single
argument style of "ok()". That is, if you try "ok(arg1,
note)", then "Test" will interpret this as "ok(arg1,
arg2)", and probably end up testing "arg1 eq arg2" --
and that's not what you want!
All of the above special cases can occasionally cause
some problems. See "BUGS and CAVEATS".
"skip(skip_if_true, args...)"
This is used for tests that under some conditions can be
skipped. It's basically equivalent to:
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if( $skip_if_true ) {
ok(1);
} else {
ok( args... );
}
...except that the ok(1) emits not just ""ok testnum""
but actually ""ok testnum # skip_if_true_value"".
The arguments after the skip_if_true are what is fed to
"ok(...)" if this test isn't skipped.
Example usage:
my $if_MSWin =
$^O =~ m/MSWin/ ? 'Skip if under MSWin' : '';
# A test to be skipped if under MSWin (i.e., run except under MSWin)
skip($if_MSWin, thing($foo), thing($bar) );
Or, going the other way:
my $unless_MSWin =
$^O =~ m/MSWin/ ? '' : 'Skip unless under MSWin';
# A test to be skipped unless under MSWin (i.e., run only under MSWin)
skip($unless_MSWin, thing($foo), thing($bar) );
The tricky thing to remember is that the first parameter
is true if you want to skip the test, not run it; and it
also doubles as a note about why it's being skipped. So
in the first codeblock above, read the code as "skip if
MSWin -- (otherwise) test whether "thing($foo)" is
"thing($bar)"" or for the second case, "skip unless
MSWin...".
Also, when your skip_if_reason string is true, it really
should (for backwards compatibility with older Test.pm
versions) start with the string "Skip", as shown in the
above examples.
Note that in the above cases, "thing($foo)" and
"thing($bar)" are evaluated -- but as long as the
"skip_if_true" is true, then we "skip(...)" just tosses
out their value (i.e., not bothering to treat them like
values to "ok(...)". But if you need to not eval the
arguments when skipping the test, use this format:
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skip( $unless_MSWin,
sub {
# This code returns true if the test passes.
# (But it doesn't even get called if the test is skipped.)
thing($foo) eq thing($bar)
}
);
or even this, which is basically equivalent:
skip( $unless_MSWin,
sub { thing($foo) }, sub { thing($bar) }
);
That is, both are like this:
if( $unless_MSWin ) {
ok(1); # but it actually appends "# $unless_MSWin"
# so that Test::Harness can tell it's a skip
} else {
# Not skipping, so actually call and evaluate...
ok( sub { thing($foo) }, sub { thing($bar) } );
}
* NORMAL TESTS
These tests are expected to succeed. Usually, most or
all of your tests are in this category. If a normal
test doesn't succeed, then that means that something is
wrong.
* SKIPPED TESTS
The "skip(...)" function is for tests that might or
might not be possible to run, depending on the availa-
bility of platform-specific features. The first argu-
ment should evaluate to true (think "yes, please skip")
if the required feature is not available. After the
first argument, "skip(...)" works exactly the same way
as "ok(...)" does.
* TODO TESTS
TODO tests are designed for maintaining an executable
TODO list. These tests are expected to fail. If a TODO
test does succeed, then the feature in question
shouldn't be on the TODO list, now should it?
Packages should NOT be released with succeeding TODO
tests. As soon as a TODO test starts working, it should
be promoted to a normal test, and the newly working
feature should be documented in the release notes or in
the change log.
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BEGIN { plan test => 4, onfail => sub { warn "CALL 911!" } }
Although test failures should be enough, extra diagnostics
can be triggered at the end of a test run. "onfail" is
passed an array ref of hash refs that describe each test
failure. Each hash will contain at least the following
fields: "package", "repetition", and "result". (You
shouldn't rely on any other fields being present.) If the
test had an expected value or a diagnostic (or "note")
string, these will also be included.
The optional "onfail" hook might be used simply to print out
the version of your package and/or how to report problems.
It might also be used to generate extremely sophisticated
diagnostics for a particularly bizarre test failure. How-
ever it's not a panacea. Core dumps or other unrecoverable
errors prevent the "onfail" hook from running. (It is run
inside an "END" block.) Besides, "onfail" is probably over-
kill in most cases. (Your test code should be simpler than
the code it is testing, yes?)
+ "ok(...)"'s special handing of strings which look like
they might be regexes can also cause unexpected
behavior. An innocent:
ok( $fileglob, '/path/to/some/*stuff/' );
will fail, since Test.pm considers the second argument
to be a regex! The best bet is to use the one-argument
form:
ok( $fileglob eq '/path/to/some/*stuff/' );
+ "ok(...)"'s use of string "eq" can sometimes cause odd
problems when comparing numbers, especially if you're
casting a string to a number:
$foo = "1.0";
ok( $foo, 1 ); # not ok, "1.0" ne 1
Your best bet is to use the single argument form:
ok( $foo == 1 ); # ok "1.0" == 1
+ As you may have inferred from the above documentation
and examples, "ok"'s prototype is "($;$$)" (and,
incidentally, "skip"'s is "($;$$$)"). This means, for
example, that you can do "ok @foo, @bar" to compare the
size of the two arrays. But don't be fooled into think-
ing that "ok @foo, @bar" means a comparison of the
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contents of two arrays -- you're comparing just the
number of elements of each. It's so easy to make that
mistake in reading "ok @foo, @bar" that you might want
to be very explicit about it, and instead write "ok
scalar(@foo), scalar(@bar)".
+ This almost definitely doesn't do what you expect:
ok $thingy->can('some_method');
Why? Because "can" returns a coderef to mean "yes it
can (and the method is this...)", and then "ok" sees a
coderef and thinks you're passing a function that you
want it to call and consider the truth of the result of!
I.e., just like:
ok $thingy->can('some_method')->();
What you probably want instead is this:
ok $thingy->can('some_method') && 1;
If the "can" returns false, then that is passed to "ok".
If it returns true, then the larger expression
"$thingy->can('some_method') && 1" returns 1, which "ok"
sees as a simple signal of success, as you would expect.
+ The syntax for "skip" is about the only way it can be,
but it's still quite confusing. Just start with the
above examples and you'll be okay.
Moreover, users may expect this:
skip $unless_mswin, foo($bar), baz($quux);
to not evaluate "foo($bar)" and "baz($quux)" when the
test is being skipped. But in reality, they are
evaluated, but "skip" just won't bother comparing them
if $unless_mswin is true.
You could do this:
skip $unless_mswin, sub{foo($bar)}, sub{baz($quux)};
But that's not terribly pretty. You may find it simpler
or clearer in the long run to just do things like this:
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if( $^O =~ m/MSWin/ ) {
print "# Yay, we're under $^O\n";
ok foo($bar), baz($quux);
ok thing($whatever), baz($stuff);
ok blorp($quux, $whatever);
ok foo($barzbarz), thang($quux);
} else {
print "# Feh, we're under $^O. Watch me skip some tests...\n";
for(1 .. 4) { skip "Skip unless under MSWin" }
}
But be quite sure that "ok" is called exactly as many
times in the first block as "skip" is called in the
second block.
If "PERL_TEST_DIFF" environment variable is set, it will be
used as a command for comparing unexpected multiline
results. If you have GNU diff installed, you might want to
set "PERL_TEST_DIFF" to "diff -u". If you don't have a suit-
able program, you might install the "Text::Diff" module and
then set "PERL_TEST_DIFF" to be "perl -MText::Diff -e 'print
diff(@ARGV)'". If "PERL_TEST_DIFF" isn't set but the
"Algorithm::Diff" module is available, then it will be used
to show the differences in multiline results.
A past developer of this module once said that it was no
longer being actively developed. However, rumors of its
demise were greatly exaggerated. Feedback and suggestions
are quite welcome.
Be aware that the main value of this module is its simpli-
city. Note that there are already more ambitious modules
out there, such as Test::More and Test::Unit.
Some earlier versions of this module had docs with some
confusing typoes in the description of "skip(...)".
Test::Harness
Test::Simple, Test::More, Devel::Cover
Test::Builder for building your own testing library.
Test::Unit is an interesting XUnit-style testing library.
Test::Inline and SelfTest let you embed tests in code.
Copyright (c) 1998-2000 Joshua Nathaniel Pritikin. All
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rights reserved.
Copyright (c) 2001-2002 Michael G. Schwern.
Copyright (c) 2002-2004 and counting Sean M. Burke.
Current maintainer: Sean M. Burke. <sburke@cpan.org>
This package is free software and is provided "as is"
without express or implied warranty. It may be used, redis-
tributed and/or modified under the same terms as Perl
itself.
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