Test2::API::Context(3)User Contributed Perl DocumentatioTest2::API::Context(3)
NAME
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. 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 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 module.
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 $bool;
}
Context objects make it easy to wrap other tools that also use context.
Once you grab a context, any tool you call before releasing your
context will inherit it:
sub wrapper {
my ($bool, $name) = @_;
my $ctx = context();
$ctx->diag("wrapping my_ok");
my $out = my_ok($bool, $name);
$ctx->release; # You MUST do this!
return $out;
}
CRITICAL DETAILS
you MUST always use the context() sub from Test2::API
Creating your own context via "Test2::API::Context->new()" will
almost never produce a desirable result. Use "context()" which is
exported by Test2::API.
There are a handful of cases where a tool author may want to create
a new context by hand, which is why the "new" method exists. Unless
you really know what you are doing you should avoid this.
You MUST always release the context when done with it
Releasing the context tells the system you are done with it. This
gives it a chance to run any necessary callbacks or cleanup tasks.
If you forget to release the context it will try to detect the
problem and warn you about it.
You MUST NOT pass context objects around
When you obtain a context object it is made specifically for your
tool and any tools nested within. If you pass a context around you
run the risk of polluting other tools with incorrect context
information.
If you are certain that you want a different tool to use the same
context you may pass it a snapshot. "$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 instance the context used to
find the current hub.
$hub = $ctx->hub()
This will return the Test2::Hub 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 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.
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. You may
optionally provide a $name for the assertion.
The Test2::Event::Pass 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.
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. You may optionally
provide a $name and @diagnostics messages.
Diagnostics messages can be simple strings, data structures, or
instances of Test2::EventFacet::Info::Table (which are converted
inline into the Test2::EventFacet::Info 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.
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 and Test2::Event::Fail
events. These newer event types are faster and less crufty.
This will create an Test2::Event::Ok object for you. If $bool is
false then an Test2::Event::Diag 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. This event prints a message to STDOUT.
$event = $ctx->diag($message)
Send an Test2::Event::Diag. 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. 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.
$event = $ctx->bail($reason)
This sends an Test2::Event::Bail 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.
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()".
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.
my $event = $ctx->send_event('Ok', ...);
or
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()".
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.
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.
$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.
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.
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.
$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.
my $ctx = context(on_release => sub {
my $ctx = shift;
...
});
THIRD PARTY META-DATA
This object consumes Test2::Util::ExternalMeta 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 AT cpan.org>
AUTHORS
Chad Granum <exodist AT cpan.org>
Kent Fredric <kentnl AT cpan.org>
COPYRIGHT
Copyright 2019 Chad Granum <exodist AT 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 v5.16.3 2019-09-06 Test2::API::Context(3)
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