=pod

=head1 NAME

B<Test::Expander> - Expansion of test functionalities that appear to be frequently used while testing.

=head1 SYNOPSIS

  # Tries to determine both class and method to be tested automatically,
  # does not create any temporary directory:
  use Test::Expander;

  # Tries to determine both class and method to be tested automatically,
  # does not create any temporary directory,
  # passes the option '-srand' to Test::V0 changing the random seed to the current time in seconds:
  use Test::Expander -srand => time;

  # Tries to determine only the method to be tested automatically, class is explicitly supplied,
  # a temporary directory is created with name corresponing to the template supplied:
  use Test::Expander -target => 'My::Class', -tempdir => { TEMPLATE => 'my_dir.XXXXXXXX' };

=head1 DESCRIPTION

B<Test::Expander> combines all advanced possibilities provided by L<Test2::V0|https://metacpan.org/pod/Test2::V0>
with some specific functions available in the older module L<Test::More|https://metacpan.org/pod/Test::More> only
(which allows a smooth migration from L<Test::More|https://metacpan.org/pod/Test::More>-based tests to
L<Test2::V0|https://metacpan.org/pod/Test2::V0>-based ones) and handy functions from some other modules
often used in test suites.

Furthermore, this module provides a recognition of class to be tested (see variable B<$CLASS> below) so that
in contrast to L<Test2::V0|https://metacpan.org/pod/Test2::V0> you do not need to specify this explicitly
if the path to the test file is in accordance with the name of class to be tested.

A similar recognition is provided in regard to the method / subroutine to be tested
(see variables B<$METHOD> and B<METHOD_REF> below) if the base name (without extension) of test file is
identical with the name of this method / subroutine.

Finally, a configurable setting of specific environment variables is provided so that
there is no need to hard-code this in the test itself.

For the time being the following options are accepted by B<Test::Expander>:

=over 2

=item

Options specific for this module only:

=over 2

=item

B<-target> - identical with the same-named option of L<Test2::V0|https://metacpan.org/pod/Test2::V0> and
has the same purpose namely the explicit definition of class to be tested as a value of this option;

=item

B<-tempdir> - activates creation of a temporary directory by the function B<tempdir> provided by
L<File::Temp::tempdir|https://metacpan.org/pod/File::Temp>.

=item

B<-tempfile> - activates creation of a temporary file by the method B<tempfile> provided by
L<File::Temp::tempfile|https://metacpan.org/pod/File::Temp>.

=back

=item

All other valid options (i.e. arguments starting with the dash sign B<->) are forwarded to
L<Test2::V0|https://metacpan.org/pod/Test2::V0> along with their values.

=item

If an argument cannot be recognized as an option, an exception is raised.

=back

The proper application of B<Test::Expander> implies that is is used as the very first in your unit test.

The only exception currently known is the case, when some actions performed on the module level
(e.g. determination of constants) base on results of other actions (e.g. mocking of built-ins).

To explain this let us assume that your unit test file should mock the built-in B<close>
to verify if the testee properly reacts both on its success and failure.
For this purpose a reasonable implementation might look as follows:

  my $closeSuccess = 1;
  BEGIN {
    *CORE::GLOBAL::close = sub (*) { return $closeSuccess ? CORE::close($_[0]) : 0 };
  }

  use Test::Expander;

Furthermore, the automated recognition of name of class to be tested can only work properly
if the test file is located in the corresponding subdirectory of B<t>, or B<xt>, or any other folder
containing a bunch of test files.
For instance, if the class to be tested is I<Foo::Bar::Baz>, then the folder with test files
related to this class should be B<t/>I<Foo>B</>I<Bar>B</>I<Baz> or B<xt/>I<Foo>B</>I<Bar>B</>I<Baz>
(the name of the top-level directory in this relative name - B<t>, or B<xt>, or B<my_test> is not important) -
otherwise the module name cannot be put into the exported variable B<$CLASS> and, if you want to use this variable,
should be supplied as a value of the option B<-target>:

  use Test::Expander -target => 'Foo::Bar::Baz';

What is more, the automated recognition of name of method / subroutine to be tested can only work properly
if the base name of the test file without extension (usually B<.t>) is equal to the method / subroutine
name. In other words, this recognition only works if the file containing the class mentioned above exists and
if this class has the method / subroutine with the same name as the test file base name without extension.
If this is the case, the exported variables B<$METHOD> and B<$METHOD_REF> contain the name of method / subroutine
to be tested and its reference, correspondingly, otherwise both variables are undefined.

Finally, B<Test::Expander> supports testing inside of a clean environment containing only some clearly
specified environment variables required for the particular test.
Names and values of these environment variables should be configured in files,
which names are identical with pathes to single class levels or method to be tested,
and the extension is always B<.env>.
For instance, if the test file name is B<t/Foo/Bar/Baz/myMethod.t>, the following approach is applied:

=over 2

=item

if the file B<t/Foo.env> exists, its content is used for the initialization of test environment,

=item

if the file B<t/Foo/Bar.env> exists, its content is used either for extension of test environment
initialized in the previous step or for its initialization if the file B<t/Foo.env> does not exist,

=item

if the file B<t/Foo/Bar/Baz.env> exists, its content is used either for extension of test
environment initialized in one of the previous steps or for its initialization if neither the file B<t/Foo.env> nor
the file B<t/Foo/Bar.env> exists,

=item

if the file B<t/Foo/Bar/Baz/myMethod.env> exists, its content will be used either for extension of test environment
initialized in one of the previous steps or for its initialization if no one of B<.env> files mentioned above exists.

=back

If the B<.env> files existing on different levels have identical names of environment variables,
the priority is the higher the later they have been detected.
I.e. B<VAR = 'VALUE0'> in B<t/Foo/Bar/Baz/myMethod.env> overwrites B<VAR = 'VALUE1'> in B<t/Foo/Bar/Baz.env>.

If no one of these B<.env> files exists, the environment will not be changed by B<Test::Expander>
during the execution of B<t/Foo/Bar/Baz/myMethod.t>.

An environment configuration file (B<.env> file) is a line-based text file,
which content is interpreted as follows:

=over 2

=item

if such files don't exist, the B<%ENV> hash remains unchanged;

=item

otherwise, if at least one of such files exists, the B<%ENV> gets emptied (without localization) and

=over 2

=item

lines not matching the RegEx B</^\w+\s\*=\s\*\S/> (some alphanumeric characters representing a name of
environment variable, optional blanks, the equal sign, again optional blanks and at least one non-blank
character representing the first sign of environment variable value) are skipped;

=item

in all other lines the value of the environment variable is everything from the first non-blank
character after the equal sign until end of the line;

=item

the value of the environment variable is evaluated by the L<string eval|https://perldoc.perl.org/functions/eval>
so that

=over 2

=item

constant values must be quoted;

=item

variables and subroutines must not be quoted:

  NAME_CONST = 'VALUE'
  NAME_VAR   = $KNIB::App::MyApp::Constants::ABC
  NAME_FUNC  = join(' ', $KNIB::App::MyApp::Constants::DEF)

=back

=back

=back

Another feature frequently applied inside of test suites is creation of a temporary directory / file used as an
isolated container for some testing actions.
The module options B<-tempdir> and B<-tempfile> fully synactically compatible with
L<File::Temp::tempdir|https://metacpan.org/pod/File::Temp#FUNCTIONS> /
L<File::Temp::tempfile|https://metacpan.org/pod/File::Temp#FUNCTIONS> make sure that such temporary
directory / file are created after B<use Test::Expander> and their names are stored in the variables
B<$TEMP_DIR> / B<$TEMP_FILE>, correspondingly.
Both temporary directory and file are removed by default after execution.

All functions provided by this module are exported by default. These and the exported variables are:

=over 2

=item

all functions exported by default from L<Test2::V0|https://metacpan.org/pod/Test2::V0>,

=item

all functions exported by default from L<Test::Files|https://metacpan.org/pod/Test::Files>,

=item

all functions exported by default from L<Test::Output|https://metacpan.org/pod/Test::Output>,

=item

all functions exported by default from L<Test::Warn|https://metacpan.org/pod/Test::Warn>,

=item

some functions exported by default from L<Test::More|https://metacpan.org/pod/Test::More>
and often used in older tests but not supported by L<Test2::V0|https://metacpan.org/pod/Test2::V0>:

=over 2

=item

BAIL_OUT,

=item

is_deeply,

=item

new_ok,

=item

require_ok,

=item

use_ok,

=back

=item

some functions exported by default from L<Test::Exception|https://metacpan.org/pod/Test::Exception>
and often used in older tests but not supported by L<Test2::V0|https://metacpan.org/pod/Test2::V0>:

=over 2

=item

dies_ok,

=item

explain,

=item

lives_ok,

=item

throws_ok,

=back

=item

function exported by default from L<Const::Fast|https://metacpan.org/pod/Const::Fast>:

=over 2

=item

const,

=back

=item

some functions exported by request from L<File::Temp|https://metacpan.org/pod/File::Temp>:

=over 2

=item

tempdir,

=item

tempfile,

=back

=item

some functions exported by request from L<Path::Tiny|https://metacpan.org/pod/Path::Tiny>:

=over 2

=item

cwd,

=item

path,

=back

=item

variable B<$CLASS> containing the name of class to be tested,

=item

variable B<$METHOD> containing the name of method to be tested,

=item

variable B<$METHOD_REF> containing the reference to subroutine to be tested.

=item

variable B<$TEMP_DIR> containing the name of a temporary directory created at compile time
if the option B<-tempdir> was supplied.

=item

variable B<$TEMP_FILE> containing the name of a temporary file created at compile time
if the option B<-tempfile> was supplied.

=back

All variables mentioned above are read-only if they are defined after B<use Test::Expander ...>.

=head1 AUTHOR

Jurij Fajnberg, <fajnbergj at gmail.com>

=head1 BUGS

Please report any bugs or feature requests through the web interface at
L<https://github.com/jsf116/Test-Expander/issues>.

=head1 COPYRIGHT AND LICENSE

=head2 LICENSE AND COPYRIGHT

Copyright (c) 2021 Jurij Fajnberg

This program is free software; you can redistribute it and/or modify it under the same terms
as the Perl 5 programming language system itself.

=cut