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TAP::Harness - Run test scripts with statistics


Version 3.48


This is a simple test harness which allows tests to be run and results automatically aggregated and output to STDOUT.


use TAP::Harness;
my $harness = TAP::Harness->new( \%args );


Class Methods


my %args = (
   verbosity => 1,
   lib     => [ 'lib', 'blib/lib', 'blib/arch' ],
my $harness = TAP::Harness->new( \%args );

The constructor returns a new TAP::Harness object. It accepts an optional hashref whose allowed keys are:

Any keys for which the value is undef will be ignored.

Instance Methods



Accepts an array of @tests to be run. This should generally be the names of test files, but this is not required. Each element in @tests will be passed to TAP::Parser::new() as a source. See TAP::Parser for more information.

It is possible to provide aliases that will be displayed in place of the test name by supplying the test as a reference to an array containing [ $test, $alias ]:

$harness->runtests( [ 't/foo.t', 'Foo Once' ],
                    [ 't/foo.t', 'Foo Twice' ] );

Normally it is an error to attempt to run the same test twice. Aliases allow you to overcome this limitation by giving each run of the test a unique name.

Tests will be run in the order found.

If the environment variable PERL_TEST_HARNESS_DUMP_TAP is defined it should name a directory into which a copy of the raw TAP for each test will be written. TAP is written to files named for each test. Subdirectories will be created as needed.

Returns a TAP::Parser::Aggregator containing the test results.


$harness->summary( $aggregator );

Output the summary for a TAP::Parser::Aggregator.


$harness->aggregate_tests( $aggregate, @tests );

Run the named tests and display a summary of result. Tests will be run in the order found.

Test results will be added to the supplied TAP::Parser::Aggregator. aggregate_tests may be called multiple times to run several sets of tests. Multiple Test::Harness instances may be used to pass results to a single aggregator so that different parts of a complex test suite may be run using different TAP::Harness settings. This is useful, for example, in the case where some tests should run in parallel but others are unsuitable for parallel execution.

my $formatter   = TAP::Formatter::Console->new;
my $ser_harness = TAP::Harness->new( { formatter => $formatter } );
my $par_harness = TAP::Harness->new(
    {   formatter => $formatter,
        jobs      => 9
my $aggregator = TAP::Parser::Aggregator->new;

$ser_harness->aggregate_tests( $aggregator, @ser_tests );
$par_harness->aggregate_tests( $aggregator, @par_tests );

Note that for simpler testing requirements it will often be possible to replace the above code with a single call to runtests.

Each element of the @tests array is either:

In the case of a perl test suite, typically source names are simply the file names of the test scripts to run.

When you supply a separate display name it becomes possible to run a test more than once; the display name is effectively the alias by which the test is known inside the harness. The harness doesn't care if it runs the same test more than once when each invocation uses a different name.


Called by the harness when it needs to create a TAP::Parser::Scheduler. Override in a subclass to provide an alternative scheduler. make_scheduler is passed the list of tests that was passed to aggregate_tests.


Gets or sets the number of concurrent test runs the harness is handling. By default, this value is 1 -- for parallel testing, this should be set higher.


Make a new parser and display formatter session. Typically used and/or overridden in subclasses.

my ( $parser, $session ) = $harness->make_parser;


Terminate use of a parser. Typically used and/or overridden in subclasses. The parser isn't destroyed as a result of this.


TAP::Harness is designed to be easy to configure.


TAP::Parser plugins let you change the way TAP is input to and output from the parser.

TAP::Parser::SourceHandlers handle TAP input. You can configure them and load custom handlers using the sources parameter to "new".

TAP::Formatters handle TAP output. You can load custom formatters by using the formatter_class parameter to "new". To configure a formatter, you currently need to instantiate it outside of TAP::Harness and pass it in with the formatter parameter to "new". This may be addressed by adding a formatters parameter to "new" in the future.


Module::Build version 0.30 supports TAP::Harness.

To load TAP::Harness plugins, you'll need to use the tap_harness_args parameter to new, typically from your Build.PL. For example:

    module_name        => 'MyApp',
    test_file_exts     => [qw(.t .tap .txt)],
    use_tap_harness    => 1,
    tap_harness_args   => {
        sources => {
            MyCustom => {},
            File => {
                extensions => ['.tap', '.txt'],
        formatter_class => 'TAP::Formatter::HTML',
    build_requires     => {
        'Module::Build' => '0.30',
        'TAP::Harness'  => '3.18',

See "new"


ExtUtils::MakeMaker does not support TAP::Harness out-of-the-box.


prove supports TAP::Harness plugins, and has a plugin system of its own. See "FORMATTERS" in prove, "SOURCE HANDLERS" in prove and App::Prove for more details.


If you can't configure TAP::Harness to do what you want, and you can't find an existing plugin, consider writing one.

The two primary use cases supported by TAP::Harness for plugins are input and output:

Customize how TAP gets into the parser

To do this, you can either extend an existing TAP::Parser::SourceHandler, or write your own. It's a pretty simple API, and they can be loaded and configured using the sources parameter to "new".

Customize how TAP results are output from the parser

To do this, you can either extend an existing TAP::Formatter, or write your own. Writing formatters are a bit more involved than writing a SourceHandler, as you'll need to understand the TAP::Parser API. A good place to start is by understanding how "aggregate_tests" works.

Custom formatters can be loaded configured using the formatter_class parameter to "new".


If you can't configure TAP::Harness to do exactly what you want, and writing a plugin isn't an option, consider extending it. It is designed to be (mostly) easy to subclass, though the cases when sub-classing is necessary should be few and far between.


The following methods are ones you may wish to override if you want to subclass TAP::Harness.



If you like the prove utility and TAP::Parser but you want your own harness, all you need to do is write one and provide new and runtests methods. Then you can use the prove utility like so:

prove --harness My::Test::Harness

Note that while prove accepts a list of tests (or things to be tested), new has a fairly rich set of arguments. You'll probably want to read over this code carefully to see how all of them are being used.