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Test::Harness - Run Perl standard test scripts with statistics


Version 3.48


  use Test::Harness;



Although, for historical reasons, the Test::Harness distribution takes its name from this module it now exists only to provide TAP::Harness with an interface that is somewhat backwards compatible with Test::Harness 2.xx. If you're writing new code consider using TAP::Harness directly instead.

Emulation is provided for runtests and execute_tests but the pluggable 'Straps' interface that previous versions of Test::Harness supported is not reproduced here. Straps is now available as a stand alone module: Test::Harness::Straps.

See TAP::Parser, TAP::Harness for the main documentation for this distribution.


The following functions are available.

runtests( @test_files )

This runs all the given @test_files and divines whether they passed or failed based on their output to STDOUT (details above). It prints out each individual test which failed along with a summary report and a how long it all took.

It returns true if everything was ok. Otherwise it will die() with one of the messages in the DIAGNOSTICS section.

execute_tests( tests => \@test_files, out => \*FH )

Runs all the given @test_files (just like runtests()) but doesn't generate the final report. During testing, progress information will be written to the currently selected output filehandle (usually STDOUT), or to the filehandle given by the out parameter. The out is optional.

Returns a list of two values, $total and $failed, describing the results. $total is a hash ref summary of all the tests run. Its keys and values are this:

    bonus           Number of individual todo tests unexpectedly passed
    max             Number of individual tests ran
    ok              Number of individual tests passed
    sub_skipped     Number of individual tests skipped
    todo            Number of individual todo tests

    files           Number of test files ran
    good            Number of test files passed
    bad             Number of test files failed
    tests           Number of test files originally given
    skipped         Number of test files skipped

If $total->{bad} == 0 and $total->{max} > 0, you've got a successful test.

$failed is a hash ref of all the test scripts that failed. Each key is the name of a test script, each value is another hash representing how that script failed. Its keys are these:

    name        Name of the test which failed
    estat       Script's exit value
    wstat       Script's wait status
    max         Number of individual tests
    failed      Number which failed
    canon       List of tests which failed (as string).

$failed should be empty if everything passed.


&runtests is exported by Test::Harness by default.

&execute_tests, $verbose, $switches and $debug are exported upon request.


Test::Harness sets these before executing the individual tests.


This is set to a true value. It allows the tests to determine if they are being executed through the harness or by any other means.


This is the version of Test::Harness.



Setting this adds perl command line switches to each test file run.

For example, HARNESS_PERL_SWITCHES=-T will turn on taint mode. HARNESS_PERL_SWITCHES=-MDevel::Cover will run Devel::Cover for each test.

-w is always set. You can turn this off in the test with BEGIN { $^W = 0 }.


Setting this to true will make the harness display the number of milliseconds each test took. You can also use prove's --timer switch.


If true, Test::Harness will output the verbose results of running its tests. Setting $Test::Harness::verbose will override this, or you can use the -v switch in the prove utility.


Provide additional options to the harness. Currently supported options are:


Run <n> (default 9) parallel jobs.


Try to color output. See "new" in TAP::Formatter::Base.


Will use TAP::Harness::Archive as the harness class, and save the TAP to file.tgz


Set the formatter_class of the harness being run. Since the HARNESS_OPTIONS is separated by :, we use - instead.

Multiple options may be separated by colons:

    HARNESS_OPTIONS=j9:c make test

Specifies a TAP::Harness subclass to be used in place of TAP::Harness.


Determines the Term::ANSIColor for the summary in case it is successful. This color defaults to 'green'.


Determines the Term::ANSIColor for the failure in case it is successful. This color defaults to 'red'.

Taint Mode

Normally when a Perl program is run in taint mode the contents of the PERL5LIB environment variable do not appear in @INC.

Because PERL5LIB is often used during testing to add build directories to @INC Test::Harness passes the names of any directories found in PERL5LIB as -I switches. The net effect of this is that PERL5LIB is honoured even in taint mode.




Please report any bugs or feature requests to bug-test-harness at, or through the web interface at I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.


Andy Armstrong <>

Test::Harness 2.64 (maintained by Andy Lester and on which this module is based) has this attribution:

    Either Tim Bunce or Andreas Koenig, we don't know. What we know for
    sure is, that it was inspired by Larry Wall's F<TEST> script that came
    with perl distributions for ages. Numerous anonymous contributors
    exist.  Andreas Koenig held the torch for many years, and then
    Michael G Schwern.


Copyright (c) 2007-2011, Andy Armstrong <>. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic.