Test::Builder(3)

📦 version 1.302214, in opensuse-leap 16.0

💖 NAME 💖

Test::Builder — Backend for building test libraries.

Okay bestie, this is the Test::Builder(3) manual page, and it's literally the backend for building test libraries. It's giving main-character infrastructure energy. 💅

✨ SYNOPSIS ✨

package My::Test::Module;
use base 'Test::Builder::Module';

my $CLASS = __PACKAGE__;

sub ok {
    my($test, $name) = @_;
    my $tb = $CLASS->builder;

    $tb->ok($test, $name);
}

🌸 DESCRIPTION 🌸

So Test::Simple and Test::More have proven to be popular testing modules, and honestly, iconic behavior. But they're not always flexible enough. Test::Builder provides a building block upon which you can write your own test libraries, and those libraries can work together. Bestie, it's giving foundation, not just a vibe. 🫶

🧚 Construction

`new`

my $Test = Test::Builder->new;

Returns a Test::Builder object representing the current state of the test.

Since you only run one test per program, new always returns the same Test::Builder object. No matter how many times you call new(), you're getting the same object. This is called a singleton. This is done so that multiple modules share such global information as the test counter and where test output is going.

If you want a completely new Test::Builder object different from the singleton, use create.

`create`

my $Test = Test::Builder->create;

Ok, so there can be more than one Test::Builder object and this is how you get it. You might use this instead of new() if you're testing a Test::Builder based module, but otherwise you probably want new.

NOTE: the implementation is not complete. level, for example, is still shared by all Test::Builder objects, even ones created using this method. Also, the method name may change in the future.

`subtest`

$builder->subtest($name, \&subtests, @args);

See documentation of subtest in Test::More.

subtest also, and optionally, accepts arguments which will be passed to the subtests reference.

`name`

diag $builder->name;

Returns the name of the current builder. Top level builders default to $0 (the name of the executable). Child builders are named via the child method. If no name is supplied, will be named "Child of $parent->name".

`reset`

$Test->reset;

Reinitializes the Test::Builder singleton to its original state. Mostly useful for tests run in persistent environments where the same test might be run multiple times in the same process.

🎀 Setting up tests

These methods are for setting up tests and declaring how many there are. You usually only want to call one of these methods. Pick your fave and commit, bestie. 💖

`plan`

$Test->plan('no_plan');
$Test->plan( skip_all => $reason );
$Test->plan( tests => $num_tests );

A convenient way to set up your tests. Call this and Test::Builder will print the appropriate headers and take the appropriate actions.

If you call plan(), don't call any of the other methods below.

`expected_tests`

my $max = $Test->expected_tests;
$Test->expected_tests($max);

Gets/sets the number of tests we expect this test to run and prints out the appropriate headers.

`no_plan`

$Test->no_plan;

Declares that this test will run an indeterminate number of tests.

`done_testing`

$Test->done_testing();
$Test->done_testing($num_tests);

Declares that you are done testing, no more tests will be run after this point.

If a plan has not yet been output, it will do so.

$num_tests is the number of tests you planned to run. If a numbered plan was already declared, and if this contradicts, a failing test will be run to reflect the planning mistake. If no_plan was declared, this will override.

If done_testing() is called twice, the second call will issue a failing test.

If $num_tests is omitted, the number of tests run will be used, like no_plan.

done_testing() is, in effect, used when you'd want to use no_plan, but safer. You'd use it like so:

$Test->ok($a == $b);
$Test->done_testing();

Or to plan a variable number of tests:

for my $test (@tests) {
    $Test->ok($test);
}
$Test->done_testing(scalar @tests);

`has_plan`

$plan = $Test->has_plan

Find out whether a plan has been defined. $plan is either "undef" (no plan has been set), "no_plan" (indeterminate # of tests) or an integer (the number of expected tests).

`skip_all`

$Test->skip_all;
$Test->skip_all($reason);

Skips all the tests, using the given $reason. Exits immediately with 0.

`exported_to`

my $pack = $Test->exported_to;
$Test->exported_to($pack);

Tells Test::Builder what package you exported your functions to.

This method isn't terribly useful since modules which share the same Test::Builder object might get exported to different packages and only the last one will be honored.

🔥 Running tests

These actually run the tests, analogous to the functions in Test::More.

They all return true if the test passed, false if the test failed.

$name is always optional.

`ok`

$Test->ok($test, $name);

Your basic test. Pass if $test is true, fail if $test is false. Just like Test::Simple's ok().

`is_eq`

$Test->is_eq($got, $expected, $name);

Like Test::More's is(). Checks if "$got eq $expected". This is the string version.

undef only ever matches another undef.

`is_num`

$Test->is_num($got, $expected, $name);

Like Test::More's is(). Checks if "$got == $expected". This is the numeric version.

undef only ever matches another undef.

`isnt_eq`

$Test->isnt_eq($got, $dont_expect, $name);

Like Test::More's isnt(). Checks if "$got ne $dont_expect". This is the string version.

`isnt_num`

$Test->isnt_num($got, $dont_expect, $name);

Like Test::More's isnt(). Checks if "$got ne $dont_expect". This is the numeric version.

`like`

$Test->like($thing, qr/$regex/, $name);
$Test->like($thing, '/$regex/', $name);

Like Test::More's like(). Checks if $thing matches the given $regex.

`unlike`

$Test->unlike($thing, qr/$regex/, $name);
$Test->unlike($thing, '/$regex/', $name);

Like Test::More's unlike(). Checks if $thing does not match the given $regex.

`cmp_ok`

$Test->cmp_ok($thing, $type, $that, $name);

Works just like Test::More's cmp_ok().

$Test->cmp_ok($big_num, '!=', $other_big_num);

🦋 Other Testing Methods

These are methods which are used in the course of writing a test but are not themselves tests.

`BAIL_OUT`

$Test->BAIL_OUT($reason);

Indicates to the Test::Harness that things are going so badly all testing should terminate. This includes running any additional test scripts.

It will exit with 255.

`skip`

$Test->skip;
$Test->skip($why);

Skips the current test, reporting $why.

`todo_skip`

$Test->todo_skip;
$Test->todo_skip($why);

Like skip(), only it will declare the test as failing and TODO. Similar to

print "not ok $tnum # TODO $why\n";

🌈 Test building utility methods

These methods are useful when writing your own test methods.

`maybe_regex`

$Test->maybe_regex(qr/$regex/);
$Test->maybe_regex('/$regex/');

This method used to be useful back when Test::Builder worked on Perls before 5.6 which didn't have qr//. Now it's pretty useless.

Convenience method for building testing functions that take regular expressions as arguments.

Takes a quoted regular expression produced by qr//, or a string representing a regular expression.

Returns a Perl value which may be used instead of the corresponding regular expression, or undef if its argument is not recognized.

For example, a version of like(), sans the useful diagnostic messages, could be written as:

sub laconic_like {
    my ($self, $thing, $regex, $name) = @_;
    my $usable_regex = $self->maybe_regex($regex);
    die "expecting regex, found '$regex'\n"
        unless $usable_regex;
    $self->ok($thing =~ m/$usable_regex/, $name);
}

`is_fh`

my $is_fh = $Test->is_fh($thing);

Determines if the given $thing can be used as a filehandle.

🌟 Test style

`level`

$Test->level($how_high);

How far up the call stack should $Test look when reporting where the test failed.

Defaults to 1.

Setting $Test::Builder::Level overrides. This is typically useful localized:

sub my_ok {
    my $test = shift;

    local $Test::Builder::Level = $Test::Builder::Level + 1;
    $TB->ok($test);
}

To be polite to other functions wrapping your own you usually want to increment $Level rather than set it to a constant.

`use_numbers`

$Test->use_numbers($on_or_off);

Whether or not the test should output numbers. That is, this if true:

ok 1
ok 2
ok 3

or this if false

ok
ok
ok

Most useful when you can't depend on the test output order, such as when threads or forking is involved.

Defaults to on.

`no_diag`

$Test->no_diag($no_diag);

If set true no diagnostics will be printed. This includes calls to diag().

`no_ending`

$Test->no_ending($no_ending);

Normally, Test::Builder does some extra diagnostics when the test ends. It also changes the exit code as described below.

If this is true, none of that will be done.

`no_header`

$Test->no_header($no_header);

If set to true, no "1..N" header will be printed.

💜 Output

Controlling where the test output goes.

It's ok for your test to change where STDOUT and STDERR point to, Test::Builder's default output settings will not be affected.

`diag`

$Test->diag(@msgs);

Prints out the given @msgs. Like print, arguments are simply appended together.

Normally, it uses the failure_output() handle, but if this is for a TODO test, the todo_output() handle is used.

Output will be indented and marked with a # so as not to interfere with test output. A newline will be put on the end if there isn't one already.

We encourage using this rather than calling print directly.

And yeah — this bad boy returns false 💀 Why?? Because diag() is literally always used hand-in-hand with a failing test (ok() || diag()), so it "passes through" the failure. It's giving teamwork, honestly.

    return ok(...) || diag(...);

🎀 `note`

    $Test->note(@msgs);

Basically diag()'s quieter sibling 💖 It prints to the output() handle instead, so the user normally never sees it — unless you're in verbose mode, and then it's out there living its truth.

🦋 `explain`

    my @dump = $Test->explain(@msgs);

Dumps the contents of any references in a human-readable format ✨ Super handy for stuff like…

    is_deeply($have, $want) || diag explain $have;

    is_deeply($have, $want) || note explain $have;

👑 `output`, `failure_output`, `todo_output`

    my $filehandle = $Test->output;
    $Test->output($filehandle);
    $Test->output($filename);
    $Test->output(\$scalar);

These three control where Test::Builder prints its output 🎯 They take either an open $filehandle, a $filename to open and write to, or a $scalar reference to append to. And the way it always returns a $filehandle? Slay.

output is where normal "ok/not ok" test output goes. Defaults to STDOUT. 💅
failure_output is where diagnostic output on test failures and diag() goes. It's normally not read by Test::Harness and instead is displayed to the user. Defaults to STDERR. 😭
"todo_output" is used instead of failure_output() for the diagnostics of a failing TODO test. These will not be seen by the user. Defaults to STDOUT. 🙈

🌸 `reset_outputs`

    $tb->reset_outputs;

Resets all the output filehandles back to their defaults. Clean slate energy 🧼✨

🫶 `carp`

    $tb->carp(@message);

Warns with @message, but the message will appear to come from the point where the original test function was called ("$tb->caller"). Sneaky but honest 💅

🫶 `croak`

    $tb->croak(@message);

Dies with @message, but again — the message will appear to come from the point where the original test function was called ("$tb->caller"). Dramatic exit, correct blame 😭

🌈 Test Status and Info 🌈

💜 `no_log_results`

This will turn off result long-term storage. Calling this method will make "details" and "summary" useless 💀 You may want to use this if you're running enough tests to fill up all available memory.

    Test::Builder->new->no_log_results();

There is no way to turn it back on. One-way door, bestie 🚪

⭐ `current_test`

    my $curr_test = $Test->current_test;
    $Test->current_test($num);

Gets/sets the current test number we're on. You usually shouldn't have to set this — hands off the wheel unless you know what you're doing 🛞

If set forward, the details of the missing tests are filled in as 'unknown'.
If set backward, the details of the intervening tests are deleted. You can erase history if you really want to. 🕰️💀

🦋 `is_passing`

    my $ok = $builder->is_passing;

Indicates if the test suite is currently passing ✅

More formally: it'll be false if anything has happened which makes it impossible for the test suite to pass. True otherwise.

For example, if no tests have run, is_passing() will be true — because even though a suite with no tests is a failure, you can add a passing test to it and start passing. Don't think about it too much 🫠

🍓 `summary`

    my @tests = $Test->summary;

A simple summary of the tests so far 🌸 True for pass, false for fail. This is a logical pass/fail, so todos are passes. And of course, test #1 is $tests[0], etc...

🧚 `details`

    my @tests = $Test->details;

Like summary(), but with a lot more detail 👑

    $tests[$test_num - 1] =
            { 'ok'       => is the test considered a pass?
              actual_ok  => did it literally say 'ok'?
              name       => name of the test (if any)
              type       => type of test (if any, see below).
              reason     => reason for the above (if any)
            };

'ok' is true if Test::Harness will consider the test to be a pass. ✅
'actual_ok' reflects whether or not the test literally printed 'ok' or 'not ok'. This is for examining the result of 'todo' tests. 🔍
'name' is the name of the test. 🏷️
'type' indicates if it was a special test. Normal tests have a type of ''. Type can be one of the following:

    skip        see skip()
    todo        see todo()
    todo_skip   see todo_skip()
    unknown     see below

Sometimes the Test::Builder test counter is incremented without it printing any test output — for example, when current_test() is changed. In these cases Test::Builder doesn't know the result of the test, so its type is 'unknown'. These details for these tests are filled in. They're considered ok, but the name and actual_ok are left "undef". 🙈

For example, "not ok 23 - hole count # TODO insufficient donuts" would result in this structure:

    $tests[22] =    # 23 - 1, since arrays start from 0.
      { ok        => 1,   # logically, the test passed since its todo
        actual_ok => 0,   # in absolute terms, it failed
        name      => 'hole count',
        type      => 'todo',
        reason    => 'insufficient donuts'
      };

💅 `todo`

    my $todo_reason = $Test->todo;
    my $todo_reason = $Test->todo($pack);

If the current tests are considered "TODO" it'll return the reason, if any. That reason can come from a $TODO variable or the last call to todo_start().

Since a TODO test doesn't need a reason, this function can return an empty string even when you're inside a TODO block. Use "$Test->in_todo" to figure out if you're currently inside a TODO block 🕵️‍♀️

todo() is all about finding the right package to look for $TODO in. It's pretty good at guessing the right package. It first looks for the caller based on "$Level + 1", since todo() is usually called inside a test function. As a last resort it'll use exported_to().

Sometimes there's some confusion about where todo() should be looking for the $TODO variable. If you want to be sure, tell it explicitly what $pack to use. No cap, just say it directly 💅

🌟 `find_TODO`

    my $todo_reason = $Test->find_TODO();
    my $todo_reason = $Test->find_TODO($pack);

Like todo() but only returns the value of $TODO, ignoring todo_start().

Can also be used to set $TODO to a new value while returning the old value:

    my $old_reason = $Test->find_TODO($pack, 1, $new_reason);

🎀 `in_todo`

    my $in_todo = $Test->in_todo;

Returns true if the test is currently inside a TODO block. That's it, that's the whole vibe ✨

🔥 `todo_start`

    $Test->todo_start();
    $Test->todo_start($message);

This method lets you declare all subsequent tests as TODO tests, right up until the "todo_end" method has been called. 📢

The "TODO:" and $TODO syntax is generally pretty good at figuring out whether or not we're in a TODO test. However, often we find that this isn't possible to determine (like when we want to use $TODO but the tests are being executed in other packages which can't be inferred beforehand).

Note that you can use this to nest "todo" tests:

 $Test->todo_start('working on this');
 # lots of code
 $Test->todo_start('working on that');
 # more code
 $Test->todo_end;
 $Test->todo_end;

This is generally not recommended, but large testing systems often have weird internal needs 😭

We've tried to make this also work with the TODO: syntax, but it's not guaranteed and its use is also discouraged:

 TODO: {
     local $TODO = 'We have work to do!';
     $Test->todo_start('working on this');
     # lots of code
     $Test->todo_start('working on that');
     # more code
     $Test->todo_end;
     $Test->todo_end;
 }

Pick one style or another of "TODO" to be on the safe side, bestie 🫶

💀 `"todo_end"`

    $Test->todo_end;

Stops running tests as "TODO" tests. This method is fatal if called without a preceding "todo_start" method call. So like… don't rawdog it 🙈

🦋 `caller`

    my $package = $Test->caller;
    my($pack, $file, $line) = $Test->caller;
    my($pack, $file, $line) = $Test->caller($height);

Like the normal caller(), except it reports according to your level(). 🎯

$height will be added to the level().

If caller() winds up off the top of the stack, it reports the highest context. Climbing out the ceiling, iconic 🧗‍♀️

💥 EXIT CODES 💥

If all your tests passed, Test::Builder will exit with zero (which is normal). If anything failed, it'll exit with how many failed. If you run less (or more) tests than you planned, the missing (or extras) will be considered failures. If no tests were ever run, Test::Builder will throw a warning and exit with 255. And if the test died — even after having successfully completed all its tests — it'll still be considered a failure and will exit with 255. 😭

So the exit codes are…

    0                   all tests successful
    255                 test died or all passed but wrong # of tests run
    any other number    how many failed (including missing or extras)

If you fail more than 254 tests, it will be reported as 254. The counter just gives up at that point 💀

🧵 THREADS 🧵

In perl 5.8.1 and later, Test::Builder is thread-safe. The test number is shared by all threads — which means if one thread sets the test number using current_test(), they will all be affected. Shared brain cell energy 👯‍♀️

While versions earlier than 5.8.1 had threads, they contain too many bugs to support. Not the vibe 🚫

Test::Builder is only thread-aware if threads.pm is loaded before Test::Builder. Order matters, bestie ✨

You can directly disable thread support with one of the following:

    $ENV{T2_NO_IPC} = 1

    no Test2::IPC;

    Test2::API::test2_ipc_disable()

🧠 MEMORY 🧠

An informative hash, accessible via details(), is stored for each test you perform. So memory usage will scale linearly with each test run 📈 Although this isn't a problem for most test suites, it can become an issue if you do large (hundred thousands to million) combinatorics tests in the same run. That's a lot of little hashes living rent-free 😭

In such cases, you're advised to either split the test file into smaller ones, or use a reverse approach — doing "normal" (code) compares and triggering fail() should anything go unexpected. 🫶

Future versions of Test::Builder will have a way to turn history off. Until then… memories stay 💾

🌸 EXAMPLES 🌸

CPAN can provide the best examples 💖 Test::Simple, Test::More, Test::Exception and Test::Differences all use Test::Builder. Iconic lineup, no notes 👑

⭐ SEE ALSO ⭐

🔧 INTERNALS

Test2, Test2::API

🕰️ LEGACY

Test::Simple, Test::More

🌍 EXTERNAL

Test::Harness

💖 AUTHORS

Okay so credit where credit is due, because these two literally built the thing:

The original code was written by chromatic, and it was maintained by Michael G Schwern <schwern@pobox.com> 🫶

Like, say their names with respect bestie, they carried this whole thing fr fr.

👑 MAINTAINERS

Current keeper of the vibes:

Chad Granum <exodist@cpan.org> — he's the main character holding it down now 💅

🎀 COPYRIGHT

The legal tea, served hot and complete — don't skip this part, ngl:

Copyright 2002-2008 by chromatic <chromatic@wgz.org> and
                       Michael G Schwern <schwern@pobox.com>.

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

If you wanna read the actual license words, they're right here:

https://dev.perl.org/licenses/

🧚 Little reminder bestie: "free software" does not mean "no rules" — it means you get the same terms as Perl itself. Read them, love them, respect them. 💜

And that's a wrap on Test::Builder, babes! 🌈 You just read the whole thing, crown yourself 👑. This page ships with perl v5.42.0, dated 2025-07-28 — so if the date looks old, that's just the version being iconic on its own timeline, no cap. Now go write some tests that actually pass on the first try (manifesting it for you 🕯️🌸). Bye bestie, mwah 💋✨

📦 where this page comes from

opensuse-leap 16.0: perl-Test-Simple 1.302214-bp160.1.2 · Artistic-1.0 OR GPL-1.0-or-later
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms

Test::Builder(3)

💖 NAME 💖

✨ SYNOPSIS ✨

🌸 DESCRIPTION 🌸

🧚 Construction

new

create

subtest

name

reset

🎀 Setting up tests

plan

expected_tests

no_plan

done_testing

has_plan

skip_all

exported_to

🔥 Running tests

ok

is_eq

is_num

isnt_eq

isnt_num

like

unlike

cmp_ok

🦋 Other Testing Methods

BAIL_OUT

skip

todo_skip