Test2::Manual::Anatomy::Hubs(3perl)           Perl Programmers Reference Guide


NAME
       Test2::Manual::Anatomy::Hubs - Internals documentation for the hub
       stack, and hubs.

DESCRIPTION
       This document describes the hub stack, and the hubs it contains. It
       explains why we have a stack, and when to add/remove hubs from it.

WHAT IS A HUB?
       Test2 is an event system, tools generate events, those events are then
       processed to modify the testing state (number of tests, number of
       failures, etc). The hub is responsible for receiving and processing
       events to record the change in state. All events should eventually
       reach a destination hub.

       The base hub is Test2::Hub. All hub classes should inherit from the
       base hub class. The base hub class provides several hooks that allow
       you to monitor or modify events. Hubs are also responsible for
       forwarding events to the output formatter.

WHY DO WE HAVE A HUB STACK?
       There are cases where it makes sense to have more than one hub:

       subtests
           In Test2 subtests are implemented using the hub stack. When you
           start a subtest a new Test2::Hub::Subtest instance is created and
           pushed to the stack. Once this is done all calls to
           "Test2::API::context" will find the new hub and send all events to
           it. When the subtest tool is complete it will remove the new hub,
           and send a final subtest event to the parent hub.

       testing your test tools
           Test2::API::intercept() is implemented using the hub stack. The
           Test2::API::intercept() function will add an
           Test2::Hub::Interceptor instance to the stack, any calls to
           Test2::API::context() will find the new hub, and send it all
           events. The intercept hub is special in that is has no connection
           to the parent hub, and usually does not have a formatter.

WHEN SHOULD I ADD A HUB TO THE STACK?
       Any time you want to intercept or block events from effecting the test
       state.  Adding a new hub is essentially a way to create a sandbox where
       you have absolute control over what events do. Adding a new hub insures
       that the main test state will not be effected.

WHERE IS THE STACK?
       The stack is an instance of Test2::API::Stack. You can access the
       global hub stack using "Test2::API::test2_stack".

WHAT ABOUT THE ROOT HUB?
       The root hub is created automatically as needed. A call to
       "Test2::API::test2_stack->top()" will create the root hub if it does
       not already exist.

HOW DO HUBS HANDLE IPC?
       If the IPC system (Test2::IPC) was not loaded, then IPC is not handled
       at all. Forking or creating new threads without the IPC system can
       cause unexpected problems.

       All hubs track the PID and Thread ID that was current when they were
       created.  If an event is sent to a hub in a new process/thread the hub
       will detect this and try to forward the event along to the correct
       process/thread. This is accomplished using the IPC system.

SEE ALSO
       Test2::Manual - Primary index of the manual.

SOURCE
       The source code repository for Test2-Manual can be found at
       https://github.com/Test-More/Test2-Suite/.

MAINTAINERS
       Chad Granum <exodist@cpan.org>

AUTHORS
       Chad Granum <exodist@cpan.org>

COPYRIGHT
       Copyright 2018 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/

perl v5.40.0                      2024-09-01
                                           Test2::Manual::Anatomy::Hubs(3perl)