Test2::Manual::Tooling::Subtest - How to implement a tool that makes use of subtests.

- NAME
- DESCRIPTION
- WHICH TYPE OF SUBTEST DO I NEED?
  - SUBTEST WITH USER SUPPLIED CODEREF
  - SUBTEST WITH TOOL-SIDE CODEREF
- SEE ALSO
- SOURCE
- MAINTAINERS
- AUTHORS
- COPYRIGHT

# NAME

Test2::Manual::Tooling::Subtest - How to implement a tool that makes use of subtests.

# DESCRIPTION

Subtests are a nice way of making related events visually, and architecturally distinct.

# WHICH TYPE OF SUBTEST DO I NEED?

There are 2 types of subtest. The first type is subtests with user-supplied coderefs, such as the `subtest()` function itself. The second type is subtest that do not have any user supplied coderefs.

So which type do you need? The answer to that is simple, if you are going to let the user define the subtest with their own codeblock, you have the first type, otherwise you have the second.

In either case, you will still need use the same API function: `Test2::API::run_subtest`.

## SUBTEST WITH USER SUPPLIED CODEREF

This example will emulate the `subtest` function.

    use Test2::API qw/context run_subtest/;

    sub my_subtest {
        my ($name, $code) = @_;

        # Like any other tool, you need to acquire a context, if you do not then
        # things will not report the correct file and line number.
        my $ctx = context();

        my $bool = run_subtest($name, $code);

        $ctx->release;

        return $bool;
    }

This looks incredibly simple... and it is. `run_subtest()` does all the hard work for you. This will issue an Test2::Event::Subtest event with the results of the subtest. The subtest event itself will report to the proper file and line number due to the context you acquired (even though it does not look like you used the context.

`run_subtest()` can take additional arguments:

    run_subtest($name, $code, \%params, @args);

@args

  This allows you to pass arguments into the codeblock that gets run.

\%params

  This is a hashref of parameters. Currently there are 3 possible parameters:

  buffered => $bool

    This will turn the subtest into the new style buffered subtest. This type of subtest is recommended, but not default.

  inherit_trace => $bool

    This is used for tool-side coderefs.

  no_fork => $bool

    react to forking/threading inside the subtest itself. In general you are unlikely to need/want this parameter.

## SUBTEST WITH TOOL-SIDE CODEREF

This is particularly useful if you want to turn a tool that wraps other tools into a subtest. For this we will be using the tool we created in Test2::Manual::Tooling::Nesting.

    use Test2::API qw/context run_subtest/;

    sub check_class {
        my $class = shift;

        my $ctx = context();

        my $code = sub {
            my $obj = $class->new;
            is($obj->foo, 'foo', "got foo");
            is($obj->bar, 'bar', "got bar");
        };

        my $bool = run_subtest($class, $code, {buffered => 1, inherit_trace => 1});

        $ctx->release;

        return $bool;
    }

The `run_subtest()` function does all the heavy lifting for us. All we need to do is give the function a name, a coderef to run, and the `inherit_trace => 1` parameter. The `buffered => 1` parameter is optional, but recommended.

The `inherit_trace` parameter tells the subtest tool that the contexts acquired inside the nested tools should use the same trace as the subtest itself. For user-supplied codeblocks you do not use inherit_trace because you want errors to report to the user-supplied file+line.

# 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/

Test2::Manual::Tooling::Subtest - How to implement a tool that makes use of subtests.