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Test2::API(3pm)        Perl Programmers Reference Guide        Test2::API(3pm)


       Test2::API - Primary interface for writing Test2 based testing tools.


       The internals of this package are subject to change at any time! The
       public methods provided will not change in backwards-incompatible ways
       (once there is a stable release), but the underlying implementation
       details might.  Do not break encapsulation here!

       Currently the implementation is to create a single instance of the
       Test2::API::Instance Object. All class methods defer to the single
       instance. There is no public access to the singleton, and that is
       intentional.  The class methods provided by this package provide the
       only functionality publicly exposed.

       This is done primarily to avoid the problems Test::Builder had by
       exposing its singleton. We do not want anyone to replace this
       singleton, rebless it, or directly muck with its internals. If you need
       to do something and cannot because of the restrictions placed here,
       then please report it as an issue. If possible, we will create a way
       for you to implement your functionality without exposing things that
       should not be exposed.


       This package exports all the functions necessary to write and/or verify
       testing tools. Using these building blocks you can begin writing test
       tools very quickly. You are also provided with tools that help you to
       test the tools you write.


       The "context()" method is your primary interface into the Test2

           package My::Ok;
           use Test2::API qw/context/;

           our @EXPORT = qw/my_ok/;
           use base 'Exporter';

           # Just like ok() from Test::More
           sub my_ok($;$) {
               my ($bool, $name) = @_;
               my $ctx = context(); # Get a context
               $ctx->ok($bool, $name);
               $ctx->release; # Release the context
               return $bool;

       See Test2::API::Context for a list of methods available on the context

       The "intercept { ... }" tool lets you temporarily intercept all events
       generated by the test system:

           use Test2::API qw/intercept/;

           use My::Ok qw/my_ok/;

           my $events = intercept {
               # These events are not displayed
               my_ok(1, "pass");
               my_ok(0, "fail");

           my_ok(@$events == 2, "got 2 events, the pass and the fail");
           my_ok($events->[0]->pass, "first event passed");
           my_ok(!$events->[1]->pass, "second event failed");


       Normally "intercept { ... }" only intercepts events sent to the main
       hub (as added by intercept itself). Nested hubs, such as those created
       by subtests, will not be intercepted. This is normally what you will
       still see the nested events by inspecting the subtest event. However
       there are times where you want to verify each event as it is sent, in
       that case use "intercept_deep { ... }".

           my $events = intercept_Deep {
               buffered_subtest foo => sub {
                   ok(1, "pass");

       $events in this case will contain 3 items:

       The event from "ok(1, "pass")"
       The plan event for the subtest
       The subtest event itself, with the first 2 events nested inside it as

       This lets you see the order in which the events were sent, unlike
       "intercept { ... }" which only lets you see events as the main hub sees

           use Test2::API qw{

           my $init  = test2_init_done();
           my $stack = test2_stack();
           my $ipc   = test2_ipc();

           my $formatter = test2_formatter();

           ... And others ...


       All exports are optional. You must specify subs to import.

           use Test2::API qw/context intercept run_subtest/;

       This is the list of exports that are most commonly needed. If you are
       simply writing a tool, then this is probably all you need. If you need
       something and you cannot find it here, then you can also look at "OTHER
       API EXPORTS".

       These exports lack the 'test2_' prefix because of how important/common
       they are. Exports in the "OTHER API EXPORTS" section have the 'test2_'
       prefix to ensure they stand out.


       $ctx = context()
       $ctx = context(%params)

       The "context()" function will always return the current context. If
       there is already a context active, it will be returned. If there is not
       an active context, one will be generated. When a context is generated
       it will default to using the file and line number where the currently
       running sub was called from.

       Please see "CRITICAL DETAILS" in Test2::API::Context for important
       rules about what you can and cannot do with a context once it is

       Note This function will throw an exception if you ignore the context
       object it returns.

       Note On perls 5.14+ a depth check is used to insure there are no
       context leaks. This cannot be safely done on older perls due to
       <> You can
       forcefully enable it either by setting "$ENV{T2_CHECK_DEPTH} = 1" or
       "$Test2::API::DO_DEPTH_CHECK = 1" BEFORE loading Test2::API.


       All parameters to "context" are optional.

       level => $int
           If you must obtain a context in a sub deeper than your entry point
           you can use this to tell it how many EXTRA stack frames to look
           back. If this option is not provided the default of 0 is used.

               sub third_party_tool {
                   my $sub = shift;
                   ... # Does not obtain a context

               third_party_tool(sub {
                   my $ctx = context(level => 1);

       wrapped => $int
           Use this if you need to write your own tool that wraps a call to
           "context()" with the intent that it should return a context object.

               sub my_context {
                   my %params = ( wrapped => 0, @_ );
                   my $ctx = context(%params);
                   return $ctx;

               sub my_tool {
                   my $ctx = my_context();

           If you do not do this, then tools you call that also check for a
           context will notice that the context they grabbed was created at
           the same stack depth, which will trigger protective measures that
           warn you and destroy the existing context.

       stack => $stack
           Normally "context()" looks at the global hub stack. If you are
           maintaining your own Test2::API::Stack instance you may pass it in
           to be used instead of the global one.

       hub => $hub
           Use this parameter if you want to obtain the context for a specific
           hub instead of whatever one happens to be at the top of the stack.

       on_init => sub { ... }
           This lets you provide a callback sub that will be called ONLY if
           your call to "context()" generated a new context. The callback WILL
           NOT be called if "context()" is returning an existing context. The
           only argument passed into the callback will be the context object

               sub foo {
                   my $ctx = context(on_init => sub { 'will run' });

                   my $inner = sub {
                       # This callback is not run since we are getting the existing
                       # context from our parent sub.
                       my $ctx = context(on_init => sub { 'will NOT run' });


       on_release => sub { ... }
           This lets you provide a callback sub that will be called when the
           context instance is released. This callback will be added to the
           returned context even if an existing context is returned. If
           multiple calls to context add callbacks, then all will be called in
           reverse order when the context is finally released.

               sub foo {
                   my $ctx = context(on_release => sub { 'will run second' });

                   my $inner = sub {
                       my $ctx = context(on_release => sub { 'will run first' });

                       # Neither callback runs on this release

                   # Both callbacks run here.


       release $ctx;
       release $ctx, ...;

       This is intended as a shortcut that lets you release your context and
       return a value in one statement. This function will get your context,
       and an optional return value. It will release your context, then return
       your value. Scalar context is always assumed.

           sub tool {
               my $ctx = context();

               return release $ctx, 1;

       This tool is most useful when you want to return the value you get from
       calling a function that needs to see the current context:

           my $ctx = context();
           my $out = some_tool(...);
           return $out;

       We can combine the last 3 lines of the above like so:

           my $ctx = context();
           release $ctx, some_tool(...);


           sub my_tool {
               context_do {
                   my $ctx = shift;

                   my (@args) = @_;

                   $ctx->ok(1, "pass");


                   # No need to call $ctx->release, done for you on scope exit.
               } @_;

       Using this inside your test tool takes care of a lot of boilerplate for
       you. It will ensure a context is acquired. It will capture and rethrow
       any exception. It will insure the context is released when you are
       done. It preserves the subroutine call context (array, scalar, void).

       This is the safest way to write a test tool. The only two downsides to
       this are a slight performance decrease, and some extra indentation in
       your source. If the indentation is a problem for you then you can take
       a peek at the next section.


       no_context { ... };
       no_context { ... } $hid;
               sub my_tool(&) {
                   my $code = shift;
                   my $ctx = context();

                   no_context {
                       # Things in here will not see our current context, they get a new
                       # one.



       This tool will hide a context for the provided block of code. This
       means any tools run inside the block will get a completely new context
       if they acquire one. The new context will be inherited by tools nested
       below the one that acquired it.

       This will normally hide the current context for the top hub. If you
       need to hide the context for a different hub you can pass in the
       optional $hid parameter.


           my $events = intercept {
               ok(1, "pass");
               ok(0, "fail");

       This function takes a codeblock as its only argument, and it has a
       prototype.  It will execute the codeblock, intercepting any generated
       events in the process. It will return an array reference with all the
       generated event objects. All events should be subclasses of

       This is a very low-level subtest tool. This is useful for writing tools
       which produce subtests. This is not intended for people simply writing


           run_subtest($NAME, \&CODE, $BUFFERED, @ARGS)

           # or

           run_subtest($NAME, \&CODE, \%PARAMS, @ARGS)

       This will run the provided codeblock with the args in @args. This
       codeblock will be run as a subtest. A subtest is an isolated test state
       that is condensed into a single Test2::Event::Subtest event, which
       contains all events generated inside the subtest.


           The name of the subtest.

           The code to run inside the subtest.

       $BUFFERED or \%PARAMS
           If this is a simple scalar then it will be treated as a boolean for
           the 'buffered' setting. If this is a hash reference then it will be
           used as a parameters hash. The param hash will be used for hub
           construction (with the specified keys removed).

           Keys that are removed and used by run_subtest:

           'buffered' => $bool
               Toggle buffered status.

           'inherit_trace' => $bool
               Normally the subtest hub is pushed and the sub is allowed to
               generate its own root context for the hub. When this setting is
               turned on a root context will be created for the hub that
               shares the same trace as the current context.

               Set this to true if your tool is producing subtests without
               user-specified subs.

           'no_fork' => $bool
               Defaults to off. Normally forking inside a subtest will
               actually fork the subtest, resulting in 2 final subtest events.
               This parameter will turn off that behavior, only the original
               process/thread will return a final subtest event.

           Any extra arguments you want passed into the subtest code.


       Normally all events inside and outside a subtest are sent to the
       formatter immediately by the hub. Sometimes it is desirable to hold off
       sending events within a subtest until the subtest is complete. This
       usually depends on the formatter being used.

       Things not effected by this flag
           In both cases events are generated and stored in an array. This
           array is eventually used to populate the "subevents" attribute on
           the Test2::Event::Subtest event that is generated at the end of the
           subtest.  This flag has no effect on this part, it always happens.

           At the end of the subtest, the final Test2::Event::Subtest event is
           sent to the formatter.

       Things that are effected by this flag
           The "buffered" attribute of the Test2::Event::Subtest event will be
           set to the value of this flag. This means any formatter, listener,
           etc which looks at the event will know if it was buffered.

       Things that are formatter dependant
           Events within a buffered subtest may or may not be sent to the
           formatter as they happen. If a formatter fails to specify then the
           default is to NOT SEND the events as they are generated, instead
           the formatter can pull them from the "subevents" attribute.

           A formatter can specify by implementing the "hide_buffered()"
           method. If this method returns true then events generated inside a
           buffered subtest will not be sent independently of the final
           subtest event.

       An example of how this is used is the Test2::Formatter::TAP formatter.
       For unbuffered subtests the events are rendered as they are generated.
       At the end of the subtest, the final subtest event is rendered, but the
       "subevents" attribute is ignored. For buffered subtests the opposite
       occurs, the events are NOT rendered as they are generated, instead the
       "subevents" attribute is used to render them all at once. This is
       useful when running subtests tests in parallel, since without it the
       output from subtests would be interleaved together.


       Exports in this section are not commonly needed. These all have the
       'test2_' prefix to help ensure they stand out. You should look at the
       "MAIN API EXPORTS" section before looking here. This section is one
       where "Great power comes with great responsibility". It is possible to
       break things badly if you are not careful with these.

       All exports are optional. You need to list which ones you want at
       import time:

           use Test2::API qw/test2_init_done .../;

       These provide access to internal state and object instances.

       $bool = test2_init_done()
           This will return true if the stack and IPC instances have already
           been initialized. It will return false if they have not. Init
           happens as late as possible. It happens as soon as a tool requests
           the IPC instance, the formatter, or the stack.

       $bool = test2_load_done()
           This will simply return the boolean value of the loaded flag. If
           Test2 has finished loading this will be true, otherwise false.
           Loading is considered complete the first time a tool requests a

           This is used to toggle Test2's belief that the END phase has
           already started.  With no arguments this will set it to true. With
           arguments it will set it to the first argument's value.

           This is used to prevent the use of "caller()" in END blocks which
           can cause segfaults. This is only necessary in some persistent
           environments that may have multiple END phases.

       $bool = test2_get_is_end()
           Check if Test2 believes it is the END phase.

       $stack = test2_stack()
           This will return the global Test2::API::Stack instance. If this has
           not yet been initialized it will be initialized now.

           Disable IPC.

       $bool = test2_ipc_diabled
           Check if IPC is disabled.

       $bool = test2_ipc_wait_enabled()
           These can be used to turn IPC waiting on and off, or check the
           current value of the flag.

           Waiting is turned on by default. Waiting will cause the parent
           process/thread to wait until all child processes and threads are
           finished before exiting. You will almost never want to turn this

       $bool = test2_no_wait()
           DISCOURAGED: This is a confusing interface, it is better to use
           "test2_ipc_wait_enable()", "test2_ipc_wait_disable()" and

           This can be used to get/set the no_wait status. Waiting is turned
           on by default. Waiting will cause the parent process/thread to wait
           until all child processes and threads are finished before exiting.
           You will almost never want to turn this off.

       $fh = test2_stdout()
       $fh = test2_stderr()
           These functions return the filehandles that test output should be
           written to.  They are primarily useful when writing a custom
           formatter and code that turns events into actual output (TAP, etc.)
           They will return a dupe of the original filehandles that formatted
           output can be sent to regardless of whatever state the currently
           running test may have left STDOUT and STDERR in.

           Re-dupe the internal filehandles returned by "test2_stdout()" and
           "test2_stderr()" from the current STDOUT and STDERR.  You shouldn't
           need to do this except in very peculiar situations (for example,
           you're testing a new formatter and you need control over where the
           formatter is sending its output.)

       These are hooks that allow you to add custom behavior to actions taken
       by Test2 and tools built on top of it.

       test2_add_callback_exit(sub { ... })
           This can be used to add a callback that is called after all testing
           is done. This is too late to add additional results, the main use
           of this callback is to set the exit code.

                   sub {
                       my ($context, $exit, \$new_exit) = @_;

           The $context passed in will be an instance of Test2::API::Context.
           The $exit argument will be the original exit code before anything
           modified it.  $$new_exit is a reference to the new exit code. You
           may modify this to change the exit code. Please note that
           $$new_exit may already be different from $exit

       test2_add_callback_post_load(sub { ... })
           Add a callback that will be called when Test2 is finished loading.
           This means the callback will be run once, the first time a context
           is obtained.  If Test2 has already finished loading then the
           callback will be run immediately.

       test2_add_callback_context_acquire(sub { ... })
           Add a callback that will be called every time someone tries to
           acquire a context. This will be called on EVERY call to
           "context()". It gets a single argument, a reference to the hash of
           parameters being used the construct the context. This is your
           chance to change the parameters by directly altering the hash.

               test2_add_callback_context_acquire(sub {
                   my $params = shift;

           This is a very scary API function. Please do not use this unless
           you need to.  This is here for Test::Builder and backwards
           compatibility. This has you directly manipulate the hash instead of
           returning a new one for performance reasons.

       test2_add_callback_context_init(sub { ... })
           Add a callback that will be called every time a new context is
           created. The callback will receive the newly created context as its
           only argument.

       test2_add_callback_context_release(sub { ... })
           Add a callback that will be called every time a context is
           released. The callback will receive the released context as its
           only argument.

       test2_add_callback_pre_subtest(sub { ... })
           Add a callback that will be called every time a subtest is going to
           be run. The callback will receive the subtest name, coderef, and
           any arguments.

       @list = test2_list_context_acquire_callbacks()
           Return all the context acquire callback references.

       @list = test2_list_context_init_callbacks()
           Returns all the context init callback references.

       @list = test2_list_context_release_callbacks()
           Returns all the context release callback references.

       @list = test2_list_exit_callbacks()
           Returns all the exit callback references.

       @list = test2_list_post_load_callbacks()
           Returns all the post load callback references.

       @list = test2_list_pre_subtest_callbacks()
           Returns all the pre-subtest callback references.

       test2_add_uuid_via(sub { ... })
       $sub = test2_add_uuid_via()
           This allows you to provide a UUID generator. If provided UUIDs will
           be attached to all events, hubs, and contexts. This is useful for
           storing, tracking, and linking these objects.

           The sub you provide should always return a unique identifier. Most
           things will expect a proper UUID string, however nothing in
           Test2::API enforces this.

           The sub will receive exactly 1 argument, the type of thing being
           tagged 'context', 'hub', or 'event'. In the future additional
           things may be tagged, in which case new strings will be passed in.
           These are purely informative, you can (and usually should) ignore

       These let you access, or specify, the IPC system internals.

       $bool = test2_has_ipc()
           Check if IPC is enabled.

       $ipc = test2_ipc()
           This will return the global Test2::IPC::Driver instance. If this
           has not yet been initialized it will be initialized now.

           Add an IPC driver to the list. This will add the driver to the
           start of the list.

       @drivers = test2_ipc_drivers()
           Get the list of IPC drivers.

       $bool = test2_ipc_polling()
           Check if polling is enabled.

           Turn on polling. This will cull events from other processes and
           threads every time a context is created.

           Turn off IPC polling.

           Turn on IPC SHM. Only some IPC drivers use this, and most will turn
           it on themselves.

           Tell other processes and events that an event is pending. $uniq_val
           should be a unique value no other thread/process will generate.

           Note: After calling this "test2_ipc_get_pending()" will return 1.
           This is intentional, and not avoidable.

       $pending = test2_ipc_get_pending()
           This returns -1 if there is no way to check (assume yes)

           This returns 0 if there are (most likely) no pending events.

           This returns 1 if there are (likely) pending events. Upon return it
           will reset, nothing else will be able to see that there were
           pending events.

       $timeout = test2_ipc_get_timeout()
           Get/Set the timeout value for the IPC system. This timeout is how
           long the IPC system will wait for child processes and threads to
           finish before aborting.

           The default value is 30 seconds.

       These let you access, or specify, the formatters that can/should be

       $formatter = test2_formatter
           This will return the global formatter class. This is not an
           instance. By default the formatter is set to Test2::Formatter::TAP.

           You can override this default using the "T2_FORMATTER" environment

           Normally 'Test2::Formatter::' is prefixed to the value in the
           environment variable:

               $ T2_FORMATTER='TAP' perl test.t     # Use the Test2::Formatter::TAP formatter
               $ T2_FORMATTER='Foo' perl test.t     # Use the Test2::Formatter::Foo formatter

           If you want to specify a full module name you use the '+' prefix:

               $ T2_FORMATTER='+Foo::Bar' perl test.t     # Use the Foo::Bar formatter

           Set the global formatter class. This can only be set once. Note:
           This will override anything specified in the 'T2_FORMATTER'
           environment variable.

       @formatters = test2_formatters()
           Get a list of all loaded formatters.

           Add a formatter to the list. Last formatter added is used at
           initialization. If this is called after initialization a warning
           will be issued.


       See the "/Examples/" directory included in this distribution.


       Test2::API::Context(3) - Detailed documentation of the context object.

       Test2::IPC(3) - The IPC system used for threading/fork support.

       Test2::Formatter(3) - Formatters such as TAP live here.

       Test2::Event(3) - Events live in this namespace.

       Test2::Hub(3) - All events eventually funnel through a hub. Custom hubs
       are how "intercept()" and "run_subtest()" are implemented.


       This package has an END block. This END block is responsible for
       setting the exit code based on the test results. This end block also
       calls the callbacks that can be added to this package.


       The source code repository for Test2 can be found at


       Chad Granum <>


       Chad Granum <>


       Copyright 2018 Chad Granum <>.

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


perl v5.28.1                      2018-11-01                   Test2::API(3pm)

perl 5.28.1 - Generated Sun Jan 13 14:38:14 CST 2019
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