Test::Builder(3perl) Perl Programmers Reference Guide Test::Builder(3perl)
NAME
Test::Builder - Backend for building test libraries
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
Test::Simple and Test::More have proven to be popular testing modules,
but they're not always flexible enough. Test::Builder provides a
building block upon which to write your own test libraries which can
work together.
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.
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 its 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.
Returns false. Why? Because diag() is often used in conjunction
with a failing test ("ok() || diag()") it "passes through" the
failure.
return ok(...) || diag(...);
note
$Test->note(@msgs);
Like diag(), but it prints to the output() handle so it will not
normally be seen by the user except in verbose mode.
explain
my @dump = $Test->explain(@msgs);
Will dump the contents of any references in a human readable format.
Handy for things like...
is_deeply($have, $want) || diag explain $have;
or
is_deeply($have, $want) || note explain $have;
output
failure_output
todo_output
my $filehandle = $Test->output;
$Test->output($filehandle);
$Test->output($filename);
$Test->output(\$scalar);
These methods control where Test::Builder will print its output.
They take either an open $filehandle, a $filename to open and write
to or a $scalar reference to append to. It will always return a
$filehandle.
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 is 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.
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").
croak
$tb->croak(@message);
Dies with @message but the message will appear to come from the
point where the original test function was called ("$tb->caller").
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 are running enough tests to fill up all available memory.
Test::Builder->new->no_log_results();
There is no way to turn it back on.
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.
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 will 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.
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' is a reflection of 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 are considered ok, but the name and actual_ok
is 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 will return the
reason, if any. This reason can come from a $TODO variable or the
last call to todo_start().
Since a TODO test does not need a reason, this function can return
an empty string even when inside a TODO block. Use "$Test->in_todo"
to determine if you are currently inside a TODO block.
todo() is about finding the right package to look for $TODO in.
It's pretty good at guessing the right package to look at. It first
looks for the caller based on "$Level + 1", since todo() is usually
called inside a test function. As a last resort it will use
exported_to().
Sometimes there is 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.
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.
todo_start
$Test->todo_start();
$Test->todo_start($message);
This method allows you declare all subsequent tests as TODO tests,
up until the "todo_end" method has been called.
The "TODO:" and $TODO syntax is generally pretty good about figuring
out whether or not we're in a TODO test. However, often we find
that this is not possible to determine (such as 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.
"todo_end"
$Test->todo_end;
Stops running tests as "TODO" tests. This method is fatal if called
without a preceding "todo_start" method call.
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 report the highest
context.
EXIT CODES
If all your tests passed, Test::Builder will exit with zero (which is
normal). If anything failed it will 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. If the test died, even after having
successfully completed all its tests, it will 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.
THREADS
In perl 5.8.1 and later, Test::Builder is thread-safe. The test number
is shared by all threads. This means if one thread sets the test number
using current_test() they will all be effected.
While versions earlier than 5.8.1 had threads they contain too many bugs
to support.
Test::Builder is only thread-aware if threads.pm is loaded before
Test::Builder.
You can directly disable thread support with one of the following:
$ENV{T2_NO_IPC} = 1
or
no Test2::IPC;
or
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 is not 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.
In such cases, you are 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.
EXAMPLES
CPAN can provide the best examples. Test::Simple, Test::More,
Test::Exception and Test::Differences all use Test::Builder.
SEE ALSO
INTERNALS
Test2, Test2::API
LEGACY
Test::Simple, Test::More
EXTERNAL
Test::Harness
AUTHORS
Original code by chromatic, maintained by Michael G Schwern
<schwern@pobox.com>
MAINTAINERS
Chad Granum <exodist@cpan.org>
COPYRIGHT
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.
See <https://dev.perl.org/licenses/>
perl v5.40.1 2026-08-30 Test::Builder(3perl)
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