Test(3p) Perl Programmers Reference Guide Test(3p) #
Test(3p) Perl Programmers Reference Guide Test(3p)
NNAAMMEE #
Test - provides a simple framework for writing test scripts
SSYYNNOOPPSSIISS #
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, $bar # arguments just like for ok(...)
);
DDEESSCCRRIIPPTTIIOONN #
This module simplifies the task of writing test files for Perl modules,
such that their output is in the format that Test::Harness expects to
see.
QQUUIICCKK SSTTAARRTT GGUUIIDDEE #
To write a test for your new (and probably not even done) module, create
a new file called _t_/_t_e_s_t_._t (in a new _t directory). If you have multiple
test files, to test the "foo", "bar", and "baz" feature sets, then feel
free to call your files _t_/_f_o_o_._t, _t_/_b_a_r_._t, and _t_/_b_a_z_._t
FFuunnccttiioonnss This module defines three public functions, “plan(…)”, “ok(…)”, and “skip(…)”. By default, all three are exported by the “use Test;” statement.
"plan(...)"
BEGIN { plan %theplan; }
This should be the first thing you call in your test script. It
declares your testing plan, how many there will be, if any of them
should be allowed to fail, and so on.
Typical usage is just:
use Test;
BEGIN { plan tests => 23 }
These are the things that you can put in the parameters to plan:
"tests => _n_u_m_b_e_r"
The number of tests in your script. This means all ookk(()) and
sskkiipp(()) calls.
"todo => [_1_,_5_,_1_4]"
A reference to a list of tests which are allowed to fail. See
“TODO TESTS”. #
"onfail => sub { ... }"
"onfail => \&some_sub"
A subroutine reference to be run at the end of the test script,
if any of the tests fail. See "ONFAIL".
You must call "plan(...)" once and only once. You should call it in
a "BEGIN {...}" block, like so:
BEGIN { plan tests => 23 }
"ok(...)"
ok(1 + 1 == 2);
ok($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 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" syntax). 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(_a_r_g_1, _a_r_g_2)" compares the two scalar
values to see if they match. They match if both are undefined, or if
_a_r_g_2 is a regex that matches _a_r_g_1, 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 considered to look like a regex if its first and last
characters 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
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 parameter. Assuming that $bytecount returns 4, "ok" ends up
testing "4 eq 4". Since that's true, this test passes.
Finally, you can append an optional third argument, in "ok(_a_r_g_1,_a_r_g_2,
_n_o_t_e)", where _n_o_t_e is a string value that will be printed if the test
fails. This should be some useful information about the test,
pertaining to why it failed, and/or a description of the test. For
example:
ok( grep($_ 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(_a_r_g_1, _n_o_t_e)", then "Test" will
interpret this as "ok(_a_r_g_1, _a_r_g_2)", and probably end up testing "_a_r_g_1
eq _a_r_g_2" -- and that's not what you want!
All of the above special cases can occasionally cause some problems.
See "BUGS and CAVEATS".
"skip(_s_k_i_p___i_f___t_r_u_e, _a_r_g_s_._._.)"
This is used for tests that under some conditions can be skipped.
It's basically equivalent to:
if( $skip_if_true ) {
ok(1);
} else {
ok( args... );
}
...except that the ok(1) emits not just ""ok _t_e_s_t_n_u_m"" but actually
""ok _t_e_s_t_n_u_m # _s_k_i_p___i_f___t_r_u_e___v_a_l_u_e"".
The arguments after the _s_k_i_p___i_f___t_r_u_e 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 _s_k_i_p the test, not _r_u_n 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 _s_k_i_p___i_f___r_e_a_s_o_n 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)" _a_r_e
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 _n_o_t eval the
arguments when skipping the test, use this format:
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) } );
}
TTEESSTT TTYYPPEESS #
• 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 _w_r_o_n_g.
• SKIPPED TESTS #
The "skip(...)" function is for tests that might or might not be
possible to run, depending on the availability of platform-specific
features. The first argument should evaluate to true (think "yes,
please skip") if the required feature is _n_o_t available. After the
first argument, "skip(...)" works exactly the same way as "ok(...)"
does.
• TODO TESTS #
TODO tests are designed for maintaining an eexxeeccuuttaabbllee TTOODDOO lliisstt.
These tests are _e_x_p_e_c_t_e_d _t_o _f_a_i_l_. 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.
OONNFFAAIILL #
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 _o_p_t_i_o_n_a_l "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. However 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?)
BBUUGGSS aanndd CCAAVVEEAATTSS • “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 _s_i_z_e of the two arrays. But don't be fooled into
thinking that "ok @foo, @bar" means a comparison of the contents of
two arrays -- you're comparing _j_u_s_t 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 _a_r_e 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:
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.
EENNVVIIRROONNMMEENNTT #
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 suitable 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.
NNOOTTEE #
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 simplicity. 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 typos
in the description of "skip(...)".
SSEEEE AALLSSOO #
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 lets you embed tests in code.
AAUUTTHHOORR #
Copyright (c) 1998-2000 Joshua Nathaniel Pritikin.
Copyright (c) 2001-2002 Michael G. Schwern.
Copyright (c) 2002-2004 Sean M. Burke.
Current maintainer: Jesse Vincent. <jesse@bestpractical.com>
This package is free software and is provided "as is" without express or
implied warranty. It may be used, redistributed and/or modified under
the same terms as Perl itself.
perl v5.36.3 2019-02-13 Test(3p)