<!-- GENERATED by docs/sphinx/bin/20-reference (p5) from reference/bundled/Test2/API/Context.md. Do not edit. -->

```{index} single: Test2::API::Context
```

# Test2::API::Context

Object to represent a testing context.

## DESCRIPTION

The context object is the primary interface for authors of testing tools
written with [Test2](../../Test2.md). The context object represents the context in
which a test takes place (File and Line Number), and provides a quick way to
generate events from that context. The context object also takes care of
sending events to the correct [Test2::Hub](../Hub.md) instance.

## SYNOPSIS

In general you will not be creating contexts directly. To obtain a context you
should always use `context()` which is exported by the [Test2::API](../API.md) module.

```perl
use Test2::API qw/context/;

sub my_ok {
    my ($bool, $name) = @_;
    my $ctx = context();

    if ($bool) {
        $ctx->pass($name);
    }
    else {
        $ctx->fail($name);
    }

    $ctx->release; # You MUST do this!
    return $bool;
}
```

Context objects make it easy to wrap other tools that also use context. Once
you grab a context, any tool you call before releasing your context will
inherit it:

```perl
sub wrapper {
    my ($bool, $name) = @_;
    my $ctx = context();
    $ctx->diag("wrapping my_ok");

    my $out = my_ok($bool, $name);
    $ctx->release; # You MUST do this!
    return $out;
}
```

## CRITICAL DETAILS

- you MUST always use the context() sub from Test2::API

    Creating your own context via `Test2::API::Context->new()` will almost never
    produce a desirable result. Use `context()` which is exported by [Test2::API](../API.md).

    There are a handful of cases where a tool author may want to create a new
    context by hand, which is why the `new` method exists. Unless you really know
    what you are doing you should avoid this.

- You MUST always release the context when done with it

    Releasing the context tells the system you are done with it. This gives it a
    chance to run any necessary callbacks or cleanup tasks. If you forget to
    release the context it will try to detect the problem and warn you about it.

- You MUST NOT pass context objects around

    When you obtain a context object it is made specifically for your tool and any
    tools nested within. If you pass a context around you run the risk of polluting
    other tools with incorrect context information.

    If you are certain that you want a different tool to use the same context you
    may pass it a snapshot. `$ctx->snapshot` will give you a shallow clone of
    the context that is safe to pass around or store.

- You MUST NOT store or cache a context for later

    As long as a context exists for a given hub, all tools that try to get a
    context will get the existing instance. If you try to store the context you
    will pollute other tools with incorrect context information.

    If you are certain that you want to save the context for later, you can use a
    snapshot. `$ctx->snapshot` will give you a shallow clone of the context
    that is safe to pass around or store.

    `context()` has some mechanisms to protect you if you do cause a context to
    persist beyond the scope in which it was obtained. In practice you should not
    rely on these protections, and they are fairly noisy with warnings.

- You SHOULD obtain your context as soon as possible in a given tool

    You never know what tools you call from within your own tool will need a
    context. Obtaining the context early ensures that nested tools can find the
    context you want them to find.

## METHODS

- $ctx->done\_testing;

    Note that testing is finished. If no plan has been set this will generate a
    Plan event.

- $clone = $ctx->snapshot()

    This will return a shallow clone of the context. The shallow clone is safe to
    store for later.

- $ctx->release()

    This will release the context. This runs cleanup tasks, and several important
    hooks. It will also restore `$!`, `$?`, and `$@` to what they were when the
    context was created.

    **Note:** If a context is acquired more than once an internal refcount is kept.
    `release()` decrements the ref count, none of the other actions of
    `release()` will occur unless the refcount hits 0. This means only the last
    call to `release()` will reset `$?`, `$!`, `$@`, and run the cleanup tasks.

- $ctx->throw($message)

    This will throw an exception reporting to the file and line number of the
    context. This will also release the context for you.

- $ctx->alert($message)

    This will issue a warning from the file and line number of the context.

- $stack = $ctx->stack()

    This will return the [Test2::API::Stack](Stack.md) instance the context used to find
    the current hub.

- $hub = $ctx->hub()

    This will return the [Test2::Hub](../Hub.md) instance the context recognizes as the
    current one to which all events should be sent.

- $dbg = $ctx->trace()

    This will return the [Test2::EventFacet::Trace](../EventFacet/Trace.md) instance used by the context.

- $ctx->do\_in\_context(\\&code, @args);

    Sometimes you have a context that is not current, and you want things to use it
    as the current one. In these cases you can call
    `$ctx->do_in_context(sub { ... })`. The codeblock will be run, and
    anything inside of it that looks for a context will find the one on which the
    method was called.

    This **DOES NOT** affect context on other hubs, only the hub used by the context
    will be affected.

    ```perl
    my $ctx = ...;
    $ctx->do_in_context(sub {
        my $ctx = context(); # returns the $ctx the sub is called on
    });
    ```

    **Note:** The context will actually be cloned, the clone will be used instead of
    the original. This allows the thread id, process id, and error variables to be correct without
    modifying the original context.

- $ctx->restore\_error\_vars()

    This will set `$!`, `$?`, and `$@` to what they were when the context was
    created. There is no localization or anything done here, calling this method
    will actually set these vars.

- $! = $ctx->errno()

    The (numeric) value of `$!` when the context was created.

- $? = $ctx->child\_error()

    The value of `$?` when the context was created.

- $@ = $ctx->eval\_error()

    The value of `$@` when the context was created.

### EVENT PRODUCTION METHODS

**Which one do I use?**

The `pass*` and `fail*` are optimal if they meet your situation, using one of
them will always be the most optimal. That said they are optimal by eliminating
many features.

Method such as `ok`, and `note` are shortcuts for generating common 1-task
events based on the old API, however they are forward compatible, and easy to
use. If these meet your needs then go ahead and use them, but please check back
often for alternatives that may be added.

If you want to generate new style events, events that do many things at once,
then you want the `*ev2*` methods. These let you directly specify which facets
you wish to use.

- $event = $ctx->pass()
- $event = $ctx->pass($name)

    This will send and return an [Test2::Event::Pass](../Event/Pass.md) event. You may optionally
    provide a `$name` for the assertion.

    The [Test2::Event::Pass](../Event/Pass.md) is a specially crafted and optimized event, using
    this will help the performance of passing tests.

- $true = $ctx->pass\_and\_release()
- $true = $ctx->pass\_and\_release($name)

    This is a combination of `pass()` and `release()`. You can use this if you do
    not plan to do anything with the context after sending the event. This helps
    write more clear and compact code.

    ```perl
    sub shorthand {
        my ($bool, $name) = @_;
        my $ctx = context();
        return $ctx->pass_and_release($name) if $bool;

        ... Handle a failure ...
    }

    sub longform {
        my ($bool, $name) = @_;
        my $ctx = context();

        if ($bool) {
            $ctx->pass($name);
            $ctx->release;
            return 1;
        }

        ... Handle a failure ...
    }
    ```

- my $event = $ctx->fail()
- my $event = $ctx->fail($name)
- my $event = $ctx->fail($name, @diagnostics)

    This lets you send an [Test2::Event::Fail](../Event/Fail.md) event. You may optionally provide a
    `$name` and `@diagnostics` messages.

    Diagnostics messages can be simple strings, data structures, or instances of
    [Test2::EventFacet::Info::Table](../EventFacet/Info/Table.md) (which are converted inline into the
    [Test2::EventFacet::Info](../EventFacet/Info.md) structure).

- my $false = $ctx->fail\_and\_release()
- my $false = $ctx->fail\_and\_release($name)
- my $false = $ctx->fail\_and\_release($name, @diagnostics)

    This is a combination of `fail()` and `release()`. This can be used to write
    clearer and shorter code.

    ```perl
    sub shorthand {
        my ($bool, $name) = @_;
        my $ctx = context();
        return $ctx->fail_and_release($name) unless $bool;

        ... Handle a success ...
    }

    sub longform {
        my ($bool, $name) = @_;
        my $ctx = context();

        unless ($bool) {
            $ctx->pass($name);
            $ctx->release;
            return 1;
        }

        ... Handle a success ...
    }
    ```

- $event = $ctx->ok($bool, $name)
- $event = $ctx->ok($bool, $name, \\@on\_fail)

    **NOTE:** Use of this method is discouraged in favor of `pass()` and `fail()`
    which produce [Test2::Event::Pass](../Event/Pass.md) and [Test2::Event::Fail](../Event/Fail.md) events. These
    newer event types are faster and less crufty.

    This will create an [Test2::Event::Ok](../Event/Ok.md) object for you. If `$bool` is false
    then an [Test2::Event::Diag](../Event/Diag.md) event will be sent as well with details about the
    failure. If you do not want automatic diagnostics you should use the
    `send_event()` method directly.

    The third argument `\@on_fail`) is an optional set of diagnostics to be sent in
    the event of a test failure. Unlike with `fail()` these diagnostics must be
    plain strings, data structures are not supported.

- $event = $ctx->note($message)

    Send an [Test2::Event::Note](../Event/Note.md). This event prints a message to STDOUT.

- $event = $ctx->diag($message)

    Send an [Test2::Event::Diag](../Event/Diag.md). This event prints a message to STDERR.

- $event = $ctx->plan($max)
- $event = $ctx->plan(0, 'SKIP', $reason)

    This can be used to send an [Test2::Event::Plan](../Event/Plan.md) event. This event
    usually takes either a number of tests you expect to run. Optionally you can
    set the expected count to 0 and give the 'SKIP' directive with a reason to
    cause all tests to be skipped.

- $event = $ctx->skip($name, $reason);

    Send an [Test2::Event::Skip](../Event/Skip.md) event.

- $event = $ctx->bail($reason)

    This sends an [Test2::Event::Bail](../Event/Bail.md) event. This event will completely
    terminate all testing.

- $event = $ctx->send\_ev2(%facets)

    This lets you build and send a V2 event directly from facets. The event is
    returned after it is sent.

    This example sends a single assertion, a note (comment for stdout in
    Test::Builder talk) and sets the plan to 1.

    ```perl
    my $event = $ctx->send_event(
        plan   => {count => 1},
        assert => {pass  => 1, details => "A passing assert"},
        info => [{tag => 'NOTE', details => "This is a note"}],
    );
    ```

- $event = $ctx->build\_e2(%facets)

    This is the same as `send_ev2()`, except it builds and returns the event
    without sending it.

- $event = $ctx->send\_ev2\_and\_release($Type, %parameters)

    This is a combination of `send_ev2()` and `release()`.

    ```perl
    sub shorthand {
        my $ctx = context();
        return $ctx->send_ev2_and_release(assert => {pass => 1, details => 'foo'});
    }

    sub longform {
        my $ctx = context();
        my $event = $ctx->send_ev2(assert => {pass => 1, details => 'foo'});
        $ctx->release;
        return $event;
    }
    ```

- $event = $ctx->send\_event($Type, %parameters)

    **It is better to use send\_ev2() in new code.**

    This lets you build and send an event of any type. The `$Type` argument should
    be the event package name with `Test2::Event::` left off, or a fully
    qualified package name prefixed with a '+'. The event is returned after it is
    sent.

    ```perl
    my $event = $ctx->send_event('Ok', ...);
    ```

    or

    ```perl
    my $event = $ctx->send_event('+Test2::Event::Ok', ...);
    ```

- $event = $ctx->build\_event($Type, %parameters)

    **It is better to use build\_ev2() in new code.**

    This is the same as `send_event()`, except it builds and returns the event
    without sending it.

- $event = $ctx->send\_event\_and\_release($Type, %parameters)

    **It is better to use send\_ev2\_and\_release() in new code.**

    This is a combination of `send_event()` and `release()`.

    ```perl
    sub shorthand {
        my $ctx = context();
        return $ctx->send_event_and_release(Pass => { name => 'foo' });
    }

    sub longform {
        my $ctx = context();
        my $event = $ctx->send_event(Pass => { name => 'foo' });
        $ctx->release;
        return $event;
    }
    ```

## HOOKS

There are 2 types of hooks, init hooks, and release hooks. As the names
suggest, these hooks are triggered when contexts are created or released.

### INIT HOOKS

These are called whenever a context is initialized. That means when a new
instance is created. These hooks are **NOT** called every time something
requests a context, just when a new one is created.

#### GLOBAL

This is how you add a global init callback. Global callbacks happen for every
context for any hub or stack.

```perl
Test2::API::test2_add_callback_context_init(sub {
    my $ctx = shift;
    ...
});
```

#### PER HUB

This is how you add an init callback for all contexts created for a given hub.
These callbacks will not run for other hubs.

```perl
$hub->add_context_init(sub {
    my $ctx = shift;
    ...
});
```

#### PER CONTEXT

This is how you specify an init hook that will only run if your call to
`context()` generates a new context. The callback will be ignored if
`context()` is returning an existing context.

```perl
my $ctx = context(on_init => sub {
    my $ctx = shift;
    ...
});
```

### RELEASE HOOKS

These are called whenever a context is released. That means when the last
reference to the instance is about to be destroyed. These hooks are **NOT**
called every time `$ctx->release` is called.

#### GLOBAL

This is how you add a global release callback. Global callbacks happen for every
context for any hub or stack.

```perl
Test2::API::test2_add_callback_context_release(sub {
    my $ctx = shift;
    ...
});
```

#### PER HUB

This is how you add a release callback for all contexts created for a given
hub. These callbacks will not run for other hubs.

```perl
$hub->add_context_release(sub {
    my $ctx = shift;
    ...
});
```

#### PER CONTEXT

This is how you add release callbacks directly to a context. The callback will
**ALWAYS** be added to the context that gets returned, it does not matter if a
new one is generated, or if an existing one is returned.

```perl
my $ctx = context(on_release => sub {
    my $ctx = shift;
    ...
});
```

## THIRD PARTY META-DATA

This object consumes [Test2::Util::ExternalMeta](../Util/ExternalMeta.md) 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
[https://github.com/Test-More/test-more/](https://github.com/Test-More/test-more/).

## MAINTAINERS

- Chad Granum <exodist@cpan.org>

## AUTHORS

- Chad Granum <exodist@cpan.org>
- Kent Fredric <kentnl@cpan.org>

## COPYRIGHT

Copyright 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 [https://dev.perl.org/licenses/](https://dev.perl.org/licenses/)