# phpman > man > Test2::Hub

## NAME
    [Test2::Hub](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AHub/markdown) - The conduit through which all events flow.

## SYNOPSIS
        use [Test2::Hub](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AHub/markdown);

        my $hub = [Test2::Hub](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AHub/markdown)->new();
        $hub->send(...);

## DESCRIPTION
    The hub is the place where all events get processed and handed off to
    the formatter. The hub also tracks test state, and provides several
    hooks into the event pipeline.

## COMMON TASKS
  SENDING EVENTS
        $hub->send($event)

    The "send()" method is used to issue an event to the hub. This method
    will handle thread/fork sync, filters, listeners, TAP output, etc.

  ALTERING OR REMOVING EVENTS
    You can use either "filter()" or "pre_filter()", depending on your
    needs. Both have identical syntax, so only "filter()" is shown here.

        $hub->filter(sub {
            my ($hub, $event) = @_;

            my $action = get_action($event);

            # No action should be taken
            return $event if $action eq 'none';

            # You want your filter to remove the event
            return undef if $action eq 'delete';

            if ($action eq 'do_it') {
                my $new_event = copy_event($event);
                ... Change your copy of the event ...
                return $new_event;
            }

            die "Should not happen";
        });

    By default, filters are not inherited by child hubs. That means if you
    start a subtest, the subtest will not inherit the filter. You can change
    this behavior with the "inherit" parameter:

        $hub->filter(sub { ... }, inherit => 1);

  LISTENING FOR EVENTS
        $hub->listen(sub {
            my ($hub, $event, $number) = @_;

            ... do whatever you want with the event ...

            # return is ignored
        });

    By default listeners are not inherited by child hubs. That means if you
    start a subtest, the subtest will not inherit the listener. You can
    change this behavior with the "inherit" parameter:

        $hub->listen(sub { ... }, inherit => 1);

  POST-TEST BEHAVIORS
        $hub->follow_up(sub {
            my ($trace, $hub) = @_;

            ... do whatever you need to ...

            # Return is ignored
        });

    follow_up subs are called only once, either when done_testing is called,
    or in an END block.

  SETTING THE FORMATTER
    By default an instance of [Test2::Formatter::TAP](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AFormatter%3A%3ATAP/markdown) is created and used.

        my $old = $hub->format([My::Formatter](https://www.chedong.com/phpMan.php/perldoc/My%3A%3AFormatter/markdown)->new);

    Setting the formatter will REPLACE any existing formatter. You may set
    the formatter to undef to prevent output. The old formatter will be
    returned if one was already set. Only one formatter is allowed at a
    time.

## METHODS
    $hub->send($event)
        This is where all events enter the hub for processing.

    $hub->process($event)
        This is called by send after it does any IPC handling. You can use
        this to bypass the IPC process, but in general you should avoid
        using this.

    $old = $hub->format($formatter)
        Replace the existing formatter instance with a new one. Formatters
        must be objects that implement a "$formatter->write($event)" method.

    $sub = $hub->listen(sub { ... }, %optional_params)
        You can use this to record all events AFTER they have been sent to
        the formatter. No changes made here will be meaningful, except
        possibly to other listeners.

            $hub->listen(sub {
                my ($hub, $event, $number) = @_;

                ... do whatever you want with the event ...

                # return is ignored
            });

        Normally listeners are not inherited by child hubs such as subtests.
        You can add the "inherit => 1" parameter to allow a listener to be
        inherited.

    $hub->unlisten($sub)
        You can use this to remove a listen callback. You must pass in the
        coderef returned by the "listen()" method.

    $sub = $hub->filter(sub { ... }, %optional_params)
    $sub = $hub->pre_filter(sub { ... }, %optional_params)
        These can be used to add filters. Filters can modify, replace, or
        remove events before anything else can see them.

            $hub->filter(
                sub {
                    my ($hub, $event) = @_;

                    return $event;    # No Changes
                    return;           # Remove the event

                    # Or you can modify an event before returning it.
                    $event->modify;
                    return $event;
                }
            );

        If you are not using threads, forking, or IPC then the only
        difference between a "filter" and a "pre_filter" is that
        "pre_filter" subs run first. When you are using threads, forking, or
        IPC, pre_filters happen to events before they are sent to their
        destination proc/thread, ordinary filters happen only in the
        destination hub/thread.

        You cannot add a regular filter to a hub if the hub was created in
        another process or thread. You can always add a pre_filter.

    $hub->unfilter($sub)
    $hub->pre_unfilter($sub)
        These can be used to remove filters and pre_filters. The $sub
        argument is the reference returned by "filter()" or "pre_filter()".

    $hub->follow_op(sub { ... })
        Use this to add behaviors that are called just before the hub is
        finalized. The only argument to your codeblock will be a
        [Test2::EventFacet::Trace](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AEventFacet%3A%3ATrace/markdown) instance.

            $hub->follow_up(sub {
                my ($trace, $hub) = @_;

                ... do whatever you need to ...

                # Return is ignored
            });

        follow_up subs are called only once, ether when done_testing is
        called, or in an END block.

    $sub = $hub->add_context_acquire(sub { ... });
        Add a callback that will be called every time someone tries to
        acquire a context. It gets a single argument, a reference of 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;
                $params->{level}++;
            });

        This is a very scary API function. Please do not use this unless you
        need to. This is here for [Test::Builder](https://www.chedong.com/phpMan.php/perldoc/Test%3A%3ABuilder/markdown) and backwards compatibility.
        This has you directly manipulate the hash instead of returning a new
        one for performance reasons.

        Note Using this hook could have a huge performance impact.

        The coderef you provide is returned and can be used to remove the
        hook later.

    $hub->remove_context_acquire($sub);
        This can be used to remove a context acquire hook.

    $sub = $hub->add_context_init(sub { ... });
        This allows you to add callbacks that will trigger every time a new
        context is created for the hub. The only argument to the sub will be
        the [Test2::API::Context](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AAPI%3A%3AContext/markdown) instance that was created.

        Note Using this hook could have a huge performance impact.

        The coderef you provide is returned and can be used to remove the
        hook later.

    $hub->remove_context_init($sub);
        This can be used to remove a context init hook.

    $sub = $hub->add_context_release(sub { ... });
        This allows you to add callbacks that will trigger every time a
        context for this hub is released. The only argument to the sub will
        be the [Test2::API::Context](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AAPI%3A%3AContext/markdown) instance that was released. These will
        run in reverse order.

        Note Using this hook could have a huge performance impact.

        The coderef you provide is returned and can be used to remove the
        hook later.

    $hub->remove_context_release($sub);
        This can be used to remove a context release hook.

    $hub->cull()
        Cull any IPC events (and process them).

    $pid = $hub->pid()
        Get the process id under which the hub was created.

    $tid = $hub->tid()
        Get the thread id under which the hub was created.

    $hud = $hub->hid()
        Get the identifier string of the hub.

    $uuid = $hub->uuid()
        If UUID tagging is enabled (see [Test2::API](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AAPI/markdown)) then the hub will have a
        UUID.

    $ipc = $hub->ipc()
        Get the IPC object used by the hub.

    $hub->set_no_ending($bool)
    $bool = $hub->no_ending
        This can be used to disable auto-ending behavior for a hub. The
        auto-ending behavior is triggered by an end block and is used to
        cull IPC events, and output the final plan if the plan was 'NO
        PLAN'.

    $bool = $hub->active
    $hub->set_active($bool)
        These are used to get/set the 'active' attribute. When true this
        attribute will force "hub->finalize()" to take action even if there
        is no plan, and no tests have been run. This flag is useful for
        plugins that add follow-up behaviors that need to run even if no
        events are seen.

  STATE METHODS
    $hub->reset_state()
        Reset all state to the start. This sets the test count to 0, clears
        the plan, removes the failures, etc.

    $num = $hub->count
        Get the number of tests that have been run.

    $num = $hub->failed
        Get the number of failures (Not all failures come from a test fail,
        so this number can be larger than the count).

    $bool = $hub->ended
        True if the testing has ended. This MAY return the stack frame of
        the tool that ended the test, but that is not guaranteed.

    $bool = $hub->is_passing
    $hub->is_passing($bool)
        Check if the overall test run is a failure. Can also be used to set
        the pass/fail status.

    $hub->plan($plan)
    $plan = $hub->plan
        Get or set the plan. The plan must be an integer larger than 0, the
        string 'NO PLAN', or the string 'SKIP'.

    $bool = $hub->check_plan
        Check if the plan and counts match, but only if the tests have
        ended. If tests have not ended this will return undef, otherwise it
        will be a true/false.

## THIRD PARTY META-DATA
    This object consumes [Test2::Util::ExternalMeta](https://www.chedong.com/phpMan.php/perldoc/Test2%3A%3AUtil%3A%3AExternalMeta/markdown) which provides a
    consistent way for you to attach meta-data to instances of this class.
    This is useful for tools, plugins, and other extensions.

## SOURCE
    The source code repository for Test2 can be found at
    <http://github.com/Test-More/test-more/>.

## MAINTAINERS
    Chad Granum <<exodist@cpan.org>>

## AUTHORS
    Chad Granum <<exodist@cpan.org>>

## COPYRIGHT
    Copyright 2020 Chad Granum <<exodist@cpan.org>>.

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

    See <http://dev.perl.org/licenses/>