Test2::Manual::Anatomy::EndToEnd(3) User Contributed Perl Documentation Test2::Manual::Anatomy::EndToEnd(3)

Test2::Manual::EndToEnd - Overview of Test2 from load to finish.

This is a high level overview of everything from loading Test2 through the end of a test script.

    use Test2::API qw/context/;
You have no access to this, it is an implementation detail.
You can import these functions, or use them directly.
It waits...

The API intentionally does as little as possible. At this point something can still change the formatter, load Test2::IPC, or have other global effects that need to be done before the first Test2::API::Context is created. Once the first Test2::API::Context is created the API will finish initialization.

See "WHAT HAPPENS WHEN I ACQUIRE A CONTEXT?" for more information.

This section covers the basic workflow all tools such as "ok()" must follow.

    sub ok($$) {
        my ($bool, $name) = @_;
        my $ctx = context();
        my $event = $ctx->send_event('Ok', pass => $bool, name => $name);
        ...
        $ctx->release;
        return $bool;
    }
    ok(1, "1 is true");

    ok(1, "1 is true");
    
    my $ctx = context();

See "WHAT HAPPENS WHEN I ACQUIRE A CONTEXT?" for more information.

See "WHAT HAPPENS WHEN I SEND AN EVENT?" for more information. 

    my $event = $ctx->send_event('Ok', pass => $bool, name => $name);
See "WHAT HAPPENS WHEN I RELEASE A CONTEXT?" for more information. 

    $ctx->release();
    
    return $bool;
    

    my $ctx = context();

These actions may not happen exactly in this order, but that is an implementation detail. For the purposes of this document this order is used to help the reader understand the flow.

$!, $@, $? and $^E are captured and preserved.
Test2 makes a point to preserve the values of $!, $@, $? and $^E such that the test tools do not modify these variables unexpectedly. They are captured first thing so that they can be restored later.
The 'loaded' state means that test tools have already started running. This is important as some plugins need to take effect before any tests are run. This state change only happens the first time a context is acquired, and may trigger some hooks defined by plugins to run.
A context attaches itself to the current Test2::Hub. If there is no current hub then the root hub will be initialized. This will also initialize the hub stack if necessary.
It is possible to create global, or hub-specific hooks that fire whenever a context is acquired, these hooks will fire now. These hooks fire even if there is an existing context.
If the current hub already has a context then a clone of it will be used instead of a completely new context. This is important because it allows nested tools to inherit the context used by parent tools.
Test2 makes a point to catch mistakes in how the context is used. The stack depth is used to accomplish this. If there is an existing context the depth will be checked against the one found here. If the old context has the same stack depth, or a shallower one, it means a tool is misbehaving and did not clean up the context when it was done, in which case the old context will be cleaned up, and a warning issued.
If there is no existing context, a new one will be created using the data collected so far.
If a new context was created, context-creation hooks will fire.
$!, $@, $?, and $^E are restored.
We make sure $!, $@, $?, and $^E are unchanged at this point so that changes we made will not effect anything else. This is done in case something inside the context construction accidentally changed these vars.
You have a shiney new context object, or a clone of the existing context.

    my $event = $ctx->send_event('Ok', pass => $bool, name => $name);
The "send_event()" method will automatically load any Event package necessary. Normally "send_event()" will assume the first argument is an event class without the "Test2::Event::" prefix, which it will add for you. If you want to use an event class that is in a different namespace you can prefix the class name with a "+" to tell the tool that you are giving a fully qualified class name: 

    my $event = $ctx->send_event('+Fully::Qualified::Event', pass => $bool, name => $name);
The event object is instantiated using the provided parameters.
The hub takes over from here.
Filters are able to modify or remove events. Filters are run first, before the event can modify global test state.
If the event effects test count then the count will be incremented. If the event causes failure then the failure count will be incremented. There are a couple other ways the global state can be effected as well.
After the state is changed the hub will send the event to the formatter for rendering. This is where TAP is normally produced.
There can be any number of listeners that take action when events are processed, this happens now.

    $ctx->release;
If your tool is nested inside another, then releasing will simply destroy the copy of the context, nothing else will happen.
When a context is created it is considered 'canon'. Any context obtained by a nested tool will be considered a child context linked to the canonical one. Releasing child contexts does not do anything of note (but is still required).
Release hooks are the main motivation behind making the "release()" method, and making it a required action on the part of test tools. These are hooks that we can have called when a tool is complete. This is how plugins like Test2::Plugin::DieOnFail are implemented. If we simply had a destructor call the hooks then we would be unable to write this plugin as a "die" inside of a destructor is useless.
The main context data is cleared allowing the next tool to create a new context. This is important as the next tool very likely has a new line number.
$!, $@, $?, and $^E are restored
When a Test2 tool is complete it will restore $@, $!, $? and $^E to avoid action at a distance.

    done_testing();
If IPC is turned on, a final culling will take place.
The follow-up hooks are a way to run actions when a hub is complete. This is useful for adding cleanup tasks, or final tests to the end of a test.
The final plan event will be produced using the current test count as the number of tests planned.
This will mark the hub is complete, and will not allow new events to be processed.

Test2 has some behaviors it runs in an "END { ... }" block after tests are done running. This end block does some final checks to warn you if something went wrong. This end block also sets the exit value of the script.

A warning will be produced if Test::Builder is loaded, but has a different version compared to Test2::API. This situation can happen if you downgrade to an older Test-Simple distribution, and is a bad situation.
If there are leftover context objects they will need to be cleaned up. A leftover context is never a good thing, and usually requires a warning. A leftover context could also be the result of an exception being thrown which terminates the script, Test2 is fairly good at noticing this and not warning in these cases as the warning would simply be noise.
If IPC is active, a waiting event is sent to all child processes.
This happens only when IPC is loaded, but Test::Builder is not. This behavior is useful, but would break compatibility for legacy tests.
All hubs are finalized starting from the top. Leftover hubs are usually a bad thing, so a warning is produced if any are found.
This step is a no-op if "done_testing()" was used. If needed this will mark the root hub as finished.
This is a chance for plugins to modify the final exit value of the script.
If the test encountered any failures this will be set to a non-zero value. If possible this will be set to the number of failures, or 255 if the number is larger than 255 (the max value allowed).
Test2 is aware of many modules which were broken by Test2's release. At this point the script will check if any known-broken modules were loaded, and warn you if they were.

Note: This only happens if there were test failures. No broken module warnings are produced on a success.

Test2::Manual - Primary index of the manual.

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

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/

2020-10-22 perl v5.34.0