Module: TAP::Harness


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:

  • verbosity

    Set the verbosity level:

     1   verbose        Print individual test results to STDOUT.
     0   normal
    -1   quiet          Suppress some test output (mostly failures 
                        while tests are running).
    -2   really quiet   Suppress everything but the tests summary.
    -3   silent         Suppress everything.
  • timer

    Append run time for each test to output. Uses Time::HiRes if available.

  • failures

    Show test failures (this is a no-op if verbose is selected).

  • comments

    Show test comments (this is a no-op if verbose is selected).

  • show_count

    Update the running test count during testing.

  • normalize

    Set to a true value to normalize the TAP that is emitted in verbose modes.

  • lib

    Accepts a scalar value or array ref of scalar values indicating which paths to allowed libraries should be included if Perl tests are executed. Naturally, this only makes sense in the context of tests written in Perl.

  • switches

    Accepts a scalar value or array ref of scalar values indicating which switches should be included if Perl tests are executed. Naturally, this only makes sense in the context of tests written in Perl.

  • test_args

    A reference to an @INC style array of arguments to be passed to each test program.

    test_args => ['foo', 'bar'],

    if you want to pass different arguments to each test then you should pass a hash of arrays, keyed by the alias for each test:

    test_args => {
      my_test    => ['foo', 'bar'],
      other_test => ['baz'],
  • color

    Attempt to produce color output.

  • exec

    Typically, Perl tests are run through this. However, anything which spits out TAP is fine. You can use this argument to specify the name of the program (and optional switches) to run your tests with:

    exec => ['/usr/bin/ruby', '-w']

    You can also pass a subroutine reference in order to determine and return the proper program to run based on a given test script. The subroutine reference should expect the TAP::Harness object itself as the first argument, and the file name as the second argument. It should return an array reference containing the command to be run and including the test file name. It can also simply return undef, in which case TAP::Harness will fall back on executing the test script in Perl:

    exec => sub {
        my ( $harness, $test_file ) = @_;
        # Let Perl tests run.
        return undef if $test_file =~ /[.]t$/;
        return [ qw( /usr/bin/ruby -w ), $test_file ]
          if $test_file =~ /[.]rb$/;

    If the subroutine returns a scalar with a newline or a filehandle, it will be interpreted as raw TAP or as a TAP stream, respectively.

  • merge

    If merge is true the harness will create parsers that merge STDOUT and STDERR together for any processes they start.

  • sources

    NEW to 3.18.

    If set, sources must be a hashref containing the names of the TAP::Parser::SourceHandlers to load and/or configure. The values are a hash of configuration that will be accessible to the source handlers via "config_for" in TAP::Parser::Source.

    For example:

    sources => {
      Perl => { exec => '/path/to/custom/perl' },
      File => { extensions => [ '.tap', '.txt' ] },
      MyCustom => { some => 'config' },

    The sources parameter affects how source, tap and exec parameters are handled.

    For more details, see the sources parameter in "new" in TAP::Parser, TAP::Parser::Source, and TAP::Parser::IteratorFactory.

  • aggregator_class

    The name of the class to use to aggregate test results. The default is TAP::Parser::Aggregator.

  • version

    NEW to 3.22.

    Assume this TAP version for TAP::Parser instead of default TAP version 12.

  • formatter_class

    The name of the class to use to format output. The default is TAP::Formatter::Console, or TAP::Formatter::File if the output isn't a TTY.

  • multiplexer_class

    The name of the class to use to multiplex tests during parallel testing. The default is TAP::Parser::Multiplexer.

  • parser_class

    The name of the class to use to parse TAP. The default is TAP::Parser.

  • scheduler_class

    The name of the class to use to schedule test execution. The default is TAP::Parser::Scheduler.

  • formatter

    If set formatter must be an object that is capable of formatting the TAP output. See TAP::Formatter::Console for an example.

  • errors

    If parse errors are found in the TAP output, a note of this will be made in the summary report. To see all of the parse errors, set this argument to true:

    errors => 1
  • directives

    If set to a true value, only test results with directives will be displayed. This overrides other settings such as verbose or failures.

  • ignore_exit

    If set to a true value instruct TAP::Parser to ignore exit and wait status from test scripts.

  • jobs

    The maximum number of parallel tests to run at any time. Which tests can be run in parallel is controlled by rules. The default is to run only one test at a time.

  • rules

    A reference to a hash of rules that control which tests may be executed in parallel. If no rules are declared and CPAN::Meta::YAML is available, TAP::Harness attempts to load rules from a YAML file specified by the rulesfile parameter. If no rules file exists, the default is for all tests to be eligible to be run in parallel.

    Here some simple examples. For the full details of the data structure and the related glob-style pattern matching, see "Rules data structure" in TAP::Parser::Scheduler.

    # Run all tests in sequence, except those starting with "p"
        par => 't/p*.t'
    # Equivalent YAML file
    par: t/p*.t
    # Run all tests in parallel, except those starting with "p"
        seq => [
                  { seq => 't/p*.t' },
                  { par => '**'     },
    # Equivalent YAML file
        - seq: t/p*.t
        - par: **
    # Run some  startup tests in sequence, then some parallel tests than some
    # teardown tests in sequence.
        seq => [
            { seq => 't/startup/*.t' },
            { par => ['t/a/*.t','t/b/*.t','t/c/*.t'], }
            { seq => 't/shutdown/*.t' },
    # Equivalent YAML file
        - seq: t/startup/*.t
        - par:
            - t/a/*.t
            - t/b/*.t
            - t/c/*.t
        - seq: t/shutdown/*.t

    This is an experimental feature and the interface may change.

  • rulesfiles

    This specifies where to find a YAML file of test scheduling rules. If not provided, it looks for a default file to use. It first checks for a file given in the HARNESS_RULESFILE environment variable, then it checks for testrules.yml and then t/testrules.yml.

  • stdout

    A filehandle for catching standard output.

  • trap

    Attempt to print summary information if run is interrupted by SIGINT (Ctrl-C).

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:

  • the source name of a test to run

  • a reference to a [ source name, display name ] array

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.