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diff --git a/Master/tlpkg/tlperl/lib/TAP/Harness/Beyond.pod b/Master/tlpkg/tlperl/lib/TAP/Harness/Beyond.pod new file mode 100644 index 00000000000..b70564ec956 --- /dev/null +++ b/Master/tlpkg/tlperl/lib/TAP/Harness/Beyond.pod @@ -0,0 +1,422 @@ +=head1 NAME + +Test::Harness::Beyond - Beyond make test + +=head1 Beyond make test + +Test::Harness is responsible for running test scripts, analysing +their output and reporting success or failure. When I type +F<make test> (or F<./Build test>) for a module, Test::Harness is usually +used to run the tests (not all modules use Test::Harness but the +majority do). + +To start exploring some of the features of Test::Harness I need to +switch from F<make test> to the F<prove> command (which ships with +Test::Harness). For the following examples I'll also need a recent +version of Test::Harness installed; 3.14 is current as I write. + +For the examples I'm going to assume that we're working with a +'normal' Perl module distribution. Specifically I'll assume that +typing F<make> or F<./Build> causes the built, ready-to-install module +code to be available below ./blib/lib and ./blib/arch and that +there's a directory called 't' that contains our tests. Test::Harness +isn't hardwired to that configuration but it saves me from explaining +which files live where for each example. + +Back to F<prove>; like F<make test> it runs a test suite - but it +provides far more control over which tests are executed, in what +order and how their results are reported. Typically F<make test> +runs all the test scripts below the 't' directory. To do the same +thing with prove I type: + + prove -rb t + +The switches here are -r to recurse into any directories below 't' +and -b which adds ./blib/lib and ./blib/arch to Perl's include path +so that the tests can find the code they will be testing. If I'm +testing a module of which an earlier version is already installed +I need to be careful about the include path to make sure I'm not +running my tests against the installed version rather than the new +one that I'm working on. + +Unlike F<make test>, typing F<prove> doesn't automatically rebuild +my module. If I forget to make before prove I will be testing against +older versions of those files - which inevitably leads to confusion. +I either get into the habit of typing + + make && prove -rb t + +or - if I have no XS code that needs to be built I use the modules +below F<lib> instead + + prove -Ilib -r t + +So far I've shown you nothing that F<make test> doesn't do. Let's +fix that. + +=head2 Saved State + +If I have failing tests in a test suite that consists of more than +a handful of scripts and takes more than a few seconds to run it +rapidly becomes tedious to run the whole test suite repeatedly as +I track down the problems. + +I can tell prove just to run the tests that are failing like this: + + prove -b t/this_fails.t t/so_does_this.t + +That speeds things up but I have to make a note of which tests are +failing and make sure that I run those tests. Instead I can use +prove's --state switch and have it keep track of failing tests for +me. First I do a complete run of the test suite and tell prove to +save the results: + + prove -rb --state=save t + +That stores a machine readable summary of the test run in a file +called '.prove' in the current directory. If I have failures I can +then run just the failing scripts like this: + + prove -b --state=failed + +I can also tell prove to save the results again so that it updates +its idea of which tests failed: + + prove -b --state=failed,save + +As soon as one of my failing tests passes it will be removed from +the list of failed tests. Eventually I fix them all and prove can +find no failing tests to run: + + Files=0, Tests=0, 0 wallclock secs ( 0.00 usr + 0.00 sys = 0.00 CPU) + Result: NOTESTS + +As I work on a particular part of my module it's most likely that +the tests that cover that code will fail. I'd like to run the whole +test suite but have it prioritize these 'hot' tests. I can tell +prove to do this: + + prove -rb --state=hot,save t + +All the tests will run but those that failed most recently will be +run first. If no tests have failed since I started saving state all +tests will run in their normal order. This combines full test +coverage with early notification of failures. + +The --state switch supports a number of options; for example to run +failed tests first followed by all remaining tests ordered by the +timestamps of the test scripts - and save the results - I can use + + prove -rb --state=failed,new,save t + +See the prove documentation (type prove --man) for the full list +of state options. + +When I tell prove to save state it writes a file called '.prove' +('_prove' on Windows) in the current directory. It's a YAML document +so it's quite easy to write tools of your own that work on the saved +test state - but the format isn't officially documented so it might +change without (much) warning in the future. + +=head2 Parallel Testing + +If my tests take too long to run I may be able to speed them up by +running multiple test scripts in parallel. This is particularly +effective if the tests are I/O bound or if I have multiple CPU +cores. I tell prove to run my tests in parallel like this: + + prove -rb -j 9 t + +The -j switch enables parallel testing; the number that follows it +is the maximum number of tests to run in parallel. Sometimes tests +that pass when run sequentially will fail when run in parallel. For +example if two different test scripts use the same temporary file +or attempt to listen on the same socket I'll have problems running +them in parallel. If I see unexpected failures I need to check my +tests to work out which of them are trampling on the same resource +and rename temporary files or add locks as appropriate. + +To get the most performance benefit I want to have the test scripts +that take the longest to run start first - otherwise I'll be waiting +for the one test that takes nearly a minute to complete after all +the others are done. I can use the --state switch to run the tests +in slowest to fastest order: + + prove -rb -j 9 --state=slow,save t + +=head2 Non-Perl Tests + +The Test Anything Protocol (http://testanything.org/) isn't just +for Perl. Just about any language can be used to write tests that +output TAP. There are TAP based testing libraries for C, C++, PHP, +Python and many others. If I can't find a TAP library for my language +of choice it's easy to generate valid TAP. It looks like this: + + 1..3 + ok 1 - init OK + ok 2 - opened file + not ok 3 - appended to file + +The first line is the plan - it specifies the number of tests I'm +going to run so that it's easy to check that the test script didn't +exit before running all the expected tests. The following lines are +the test results - 'ok' for pass, 'not ok' for fail. Each test has +a number and, optionally, a description. And that's it. Any language +that can produce output like that on STDOUT can be used to write +tests. + +Recently I've been rekindling a two-decades-old interest in Forth. +Evidently I have a masochistic streak that even Perl can't satisfy. +I want to write tests in Forth and run them using prove (you can +find my gforth TAP experiments at +https://svn.hexten.net/andy/Forth/Testing/). I can use the --exec +switch to tell prove to run the tests using gforth like this: + + prove -r --exec gforth t + +Alternately, if the language used to write my tests allows a shebang +line I can use that to specify the interpreter. Here's a test written +in PHP: + + #!/usr/bin/php + <?php + print "1..2\n"; + print "ok 1\n"; + print "not ok 2\n"; + ?> + +If I save that as t/phptest.t the shebang line will ensure that it +runs correctly along with all my other tests. + +=head2 Mixing it up + +Subtle interdependencies between test programs can mask problems - +for example an earlier test may neglect to remove a temporary file +that affects the behaviour of a later test. To find this kind of +problem I use the --shuffle and --reverse options to run my tests +in random or reversed order. + +=head2 Rolling My Own + +If I need a feature that prove doesn't provide I can easily write my own. + +Typically you'll want to change how TAP gets I<input> into and I<output> +from the parser. L<App::Prove> supports arbitrary plugins, and L<TAP::Harness> +supports custom I<formatters> and I<source handlers> that you can load using +either L<prove> or L<Module::Build>; there are many examples to base mine on. +For more details see L<App::Prove>, L<TAP::Parser::SourceHandler>, and +L<TAP::Formatter::Base>. + +If writing a plugin is not enough, you can write your own test harness; one of +the motives for the 3.00 rewrite of Test::Harness was to make it easier to +subclass and extend. + +The Test::Harness module is a compatibility wrapper around TAP::Harness. +For new applications I should use TAP::Harness directly. As we'll +see, prove uses TAP::Harness. + +When I run prove it processes its arguments, figures out which test +scripts to run and then passes control to TAP::Harness to run the +tests, parse, analyse and present the results. By subclassing +TAP::Harness I can customise many aspects of the test run. + +I want to log my test results in a database so I can track them +over time. To do this I override the summary method in TAP::Harness. +I start with a simple prototype that dumps the results as a YAML +document: + + package My::TAP::Harness; + + use base 'TAP::Harness'; + use YAML; + + sub summary { + my ( $self, $aggregate ) = @_; + print Dump( $aggregate ); + $self->SUPER::summary( $aggregate ); + } + + 1; + +I need to tell prove to use my My::TAP::Harness. If My::TAP::Harness +is on Perl's @INC include path I can + + prove --harness=My::TAP::Harness -rb t + +If I don't have My::TAP::Harness installed on @INC I need to provide +the correct path to perl when I run prove: + + perl -Ilib `which prove` --harness=My::TAP::Harness -rb t + +I can incorporate these options into my own version of prove. It's +pretty simple. Most of the work of prove is handled by App::Prove. +The important code in prove is just: + + use App::Prove; + + my $app = App::Prove->new; + $app->process_args(@ARGV); + exit( $app->run ? 0 : 1 ); + +If I write a subclass of App::Prove I can customise any aspect of +the test runner while inheriting all of prove's behaviour. Here's +myprove: + + #!/usr/bin/env perl use lib qw( lib ); # Add ./lib to @INC + use App::Prove; + + my $app = App::Prove->new; + + # Use custom TAP::Harness subclass + $app->harness( 'My::TAP::Harness' ); + + $app->process_args( @ARGV ); exit( $app->run ? 0 : 1 ); + +Now I can run my tests like this + + ./myprove -rb t + +=head2 Deeper Customisation + +Now that I know how to subclass and replace TAP::Harness I can +replace any other part of the harness. To do that I need to know +which classes are responsible for which functionality. Here's a +brief guided tour; the default class for each component is shown +in parentheses. Normally any replacements I write will be subclasses +of these default classes. + +When I run my tests TAP::Harness creates a scheduler +(TAP::Parser::Scheduler) to work out the running order for the +tests, an aggregator (TAP::Parser::Aggregator) to collect and analyse +the test results and a formatter (TAP::Formatter::Console) to display +those results. + +If I'm running my tests in parallel there may also be a multiplexer +(TAP::Parser::Multiplexer) - the component that allows multiple +tests to run simultaneously. + +Once it has created those helpers TAP::Harness starts running the +tests. For each test it creates a new parser (TAP::Parser) which +is responsible for running the test script and parsing its output. + +To replace any of these components I call one of these harness +methods with the name of the replacement class: + + aggregator_class + formatter_class + multiplexer_class + parser_class + scheduler_class + +For example, to replace the aggregator I would + + $harness->aggregator_class( 'My::Aggregator' ); + +Alternately I can supply the names of my substitute classes to the +TAP::Harness constructor: + + my $harness = TAP::Harness->new( + { aggregator_class => 'My::Aggregator' } + ); + +If I need to reach even deeper into the internals of the harness I +can replace the classes that TAP::Parser uses to execute test scripts +and tokenise their output. Before running a test script TAP::Parser +creates a grammar (TAP::Parser::Grammar) to decode the raw TAP into +tokens, a result factory (TAP::Parser::ResultFactory) to turn the +decoded TAP results into objects and, depending on whether it's +running a test script or reading TAP from a file, scalar or array +a source or an iterator (TAP::Parser::IteratorFactory). + +Each of these objects may be replaced by calling one of these parser +methods: + + source_class + perl_source_class + grammar_class + iterator_factory_class + result_factory_class + +=head2 Callbacks + +As an alternative to subclassing the components I need to change I +can attach callbacks to the default classes. TAP::Harness exposes +these callbacks: + + parser_args Tweak the parameters used to create the parser + made_parser Just made a new parser + before_runtests About to run tests + after_runtests Have run all tests + after_test Have run an individual test script + +TAP::Parser also supports callbacks; bailout, comment, plan, test, +unknown, version and yaml are called for the corresponding TAP +result types, ALL is called for all results, ELSE is called for all +results for which a named callback is not installed and EOF is +called once at the end of each TAP stream. + +To install a callback I pass the name of the callback and a subroutine +reference to TAP::Harness or TAP::Parser's callback method: + + $harness->callback( after_test => sub { + my ( $script, $desc, $parser ) = @_; + } ); + +I can also pass callbacks to the constructor: + + my $harness = TAP::Harness->new({ + callbacks => { + after_test => sub { + my ( $script, $desc, $parser ) = @_; + # Do something interesting here + } + } + }); + +When it comes to altering the behaviour of the test harness there's +more than one way to do it. Which way is best depends on my +requirements. In general if I only want to observe test execution +without changing the harness' behaviour (for example to log test +results to a database) I choose callbacks. If I want to make the +harness behave differently subclassing gives me more control. + +=head2 Parsing TAP + +Perhaps I don't need a complete test harness. If I already have a +TAP test log that I need to parse all I need is TAP::Parser and the +various classes it depends upon. Here's the code I need to run a +test and parse its TAP output + + use TAP::Parser; + + my $parser = TAP::Parser->new( { source => 't/simple.t' } ); + while ( my $result = $parser->next ) { + print $result->as_string, "\n"; + } + +Alternately I can pass an open filehandle as source and have the +parser read from that rather than attempting to run a test script: + + open my $tap, '<', 'tests.tap' + or die "Can't read TAP transcript ($!)\n"; + my $parser = TAP::Parser->new( { source => $tap } ); + while ( my $result = $parser->next ) { + print $result->as_string, "\n"; + } + +This approach is useful if I need to convert my TAP based test +results into some other representation. See TAP::Convert::TET +(http://search.cpan.org/dist/TAP-Convert-TET/) for an example of +this approach. + +=head2 Getting Support + +The Test::Harness developers hang out on the tapx-dev mailing +list[1]. For discussion of general, language independent TAP issues +there's the tap-l[2] list. Finally there's a wiki dedicated to the +Test Anything Protocol[3]. Contributions to the wiki, patches and +suggestions are all welcome. + +[1] L<http://www.hexten.net/mailman/listinfo/tapx-dev> +[2] L<http://testanything.org/mailman/listinfo/tap-l> +[3] L<http://testanything.org/> |