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Test::Builder(3pm)     Perl Programmers Reference Guide     Test::Builder(3pm)


       Test::Builder - Backend for building test libraries


         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);


       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.

             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".

             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.

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

           See documentation of "subtest" in Test::More.

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

            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".


           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.

             $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

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

               my $max = $Test->expected_tests;

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


           Declares that this test will run an indeterminate number of 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);

           Or to plan a variable number of tests:

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

             $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).


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

             my $pack = $Test->exported_to;

           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.

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

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

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

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

           "undef" only ever matches another "undef".

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

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

           "undef" only ever matches another "undef".

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

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

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

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

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

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

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

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

             $Test->cmp_ok($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.


           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.


           Skips the current test, reporting $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.


           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);

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

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

   Test style

           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

               sub my_ok {
                   my $test = shift;

                   local $Test::Builder::Level = $Test::Builder::Level + 1;

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


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

             ok 1
             ok 2
             ok 3

           or this if false


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

           Defaults to on.


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


           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.


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

       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.


           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

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


           Like "diag()", but it prints to the "output()" handle so it will
           not normally be seen by the user except in verbose mode.

               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;


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

               my $filehandle = $Test->output;

           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

           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

           Defaults to STDOUT.


           Resets all the output filehandles back to their defaults.


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


           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
               my $curr_test = $Test->current_test;

           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.

              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.

               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...

               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'

               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

           "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.

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

           Like "todo()" but only returns the value of $TODO ignoring

           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);

               my $in_todo = $Test->in_todo;

           Returns true if the test is currently inside a TODO block.


           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

           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

           Pick one style or another of "TODO" to be on the safe side.


           Stops running tests as "TODO" tests.  This method is fatal if
           called without a preceding "todo_start" method call.

               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

           $height will be added to the "level()".

           If "caller()" winds up off the top of the stack it report the
           highest context.


       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.


       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 is loaded before


       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.


       CPAN can provide the best examples.  Test::Simple, Test::More,
       Test::Exception and Test::Differences all use Test::Builder.


       Test::Simple(3), Test::More(3), Test::Harness(3)


       Original code by chromatic, maintained by Michael G Schwern


       Chad Granum <>


       Copyright 2002-2008 by chromatic <> and
                              Michael G Schwern <>.

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


perl v5.26.1                      2017-07-18                Test::Builder(3pm)

perl 5.26.1 - Generated Mon Nov 6 19:02:02 CST 2017
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