Test::Harness::TAP - Documentation for the TAP format


Test::Harness::TAP - Documentation for the TAP format


Perl's interface between testing modules like Test::More and the test harness Test::Harness is a simple text-based format called TAP, the Test Anything Protocol. This is its story.


The ``interpreter'' is the program that reads and analyzes some TAP output. In Perl, this is handled by the Test::Harness module, with the runtests() function.


Perl test scripts print to standard output "ok N" for each single test, where N is an increasing sequence of integers. The first line output by a standard test script is "1..M" with M being the number of tests that should be run within the test script.

After all tests have been performed, runtests() prints some performance statistics that are computed by the Benchmark module.

The test script output

The following explains how Test::Harness interprets the output of your test program.

This header tells how many tests there will be. For example, 1..10 means you plan on running 10 tests. This is a safeguard in case your test dies quietly in the middle of its run.

It should be the first non-comment line output by your test program.

In certain instances, you may not know how many tests you will ultimately be running. In this case, it is permitted for the 1..M header to appear as the last line output by your test (again, it can be followed by further comments).

Under no circumstances should 1..M appear in the middle of your output or more than once.

'ok', 'not ok'. Ok?
Any output from the testscript to standard error is ignored and bypassed, thus will be seen by the user. Lines written to standard output containing /^(not\s+)?ok\b/ are interpreted as feedback for the TAP interpreter. All other lines are discarded.

/^not ok/ indicates a failed test. /^ok/ is a successful test.

test numbers
TAP normally expects the ``ok'' or ``not ok'' to be followed by a test number. It is tolerated if the test numbers after ``ok'' are omitted. In this case, the interpreter must temporarily maintain its own counter until the script supplies test numbers again. So the following test script
    print <<END;
    not ok
    not ok

will generate

    FAILED tests 1, 3, 6
    Failed 3/6 tests, 50.00% okay

test labels
Anything after the test number, but before the ``#'', is considered to be the label for the test.
  ok 42 this is the label of the test

Currently, Test::Harness does nothing with this information.

Skipping tests
If the standard output line contains the substring # Skip (with variations in spacing and case) after ok or ok NUMBER, it is counted as a skipped test. If the whole testscript succeeds, the count of skipped tests is included in the generated output. Test::Harness reports the text after # Skip\S*\s+ as a reason for skipping.
  ok 23 # skip Insufficient flogiston pressure.

Similarly, one can include a similar explanation in a 1..0 line emitted if the test script is skipped completely:

  1..0 # Skipped: no leverage found

Todo tests
If the standard output line contains the substring # TODO after not ok or not ok NUMBER, it is counted as a todo test. The text afterwards is the thing that has to be done before this test will succeed.
  not ok 13 # TODO harness the power of the atom

Note that the TODO must have a space after it.

These tests represent a feature to be implemented or a bug to be fixed and act as something of an executable ``thing to do'' list. They are not expected to succeed. Should a todo test begin succeeding, Test::Harness will report it as a bonus. This indicates that whatever you were supposed to do has been done and you should promote this to a normal test.

Bail out!
As an emergency measure, a test script can decide that further tests are useless (e.g. missing dependencies) and testing should stop immediately. In that case the test script prints the magic words
  Bail out!

to standard output. Any message after these words must be displayed by the interpreter as the reason why testing must be stopped.

Additional comments may be put into the testing output on their own lines. Comment lines should begin with a '#', Test::Harness will ignore them.
  ok 1
  # Life is good, the sun is shining, RAM is cheap.
  not ok 2
  # got 'Bush' expected 'Gore'

Anything else
Any other output Test::Harness sees it will silently ignore BUT WE PLAN TO CHANGE THIS! If you wish to place additional output in your test script, please use a comment.





Andy Lester, based on the original Test::Harness documentation by Michael Schwern.


Copyright 2003-2004 by Michael G Schwern <schwern@pobox.com>, Andy Lester <andy@petdance.com>.

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

See http://www.perl.com/perl/misc/Artistic.html.

 Test::Harness::TAP - Documentation for the TAP format