Michael Graham


Test::More - yet another framework for writing test scripts


  use Test::More tests => $Num_Tests;
  # or
  use Test::More qw(no_plan);
  # or
  use Test::More qw(skip_all);

  BEGIN { use_ok( 'Some::Module' ); }
  require_ok( 'Some::Module' );

  # Various ways to say "ok"
  ok($this eq $that, $test_name);

  is  ($this, $that,    $test_name);
  isnt($this, $that,    $test_name);
  like($this, qr/that/, $test_name);

  skip {                        # UNIMPLEMENTED!!!
      ok( foo(),       $test_name );
      is( foo(42), 23, $test_name );
  } $how_many, $why;

  todo {                        # UNIMPLEMENTED!!!
      ok( foo(),       $test_name );
      is( foo(42), 23, $test_name );
  } $how_many, $why;


  # Utility comparison functions.
  eq_array(\@this, \@that);
  eq_hash(\%this, \%that);
  eq_set(\@this, \@that);

  my @status = Test::More::status;


If you're just getting started writing tests, have a look at Test::Simple first.

This module provides a very wide range of testing utilities. Various ways to say "ok", facilities to skip tests, test future features and compare complicated data structures.

I love it when a plan comes together

Before anything else, you need a testing plan. This basically declares how many tests your script is going to run to protect against premature failure.

The prefered way to do this is to declare a plan when you use Test::More.

  use Test::More tests => $Num_Tests;

There are rare cases when you will not know beforehand how many tests your script is going to run. In this case, you can declare that you have no plan. (Try to avoid using this as it weakens your test.)

  use Test::More qw(no_plan);

In some cases, you'll want to completely skip an entire testing script.

  use Test::More qw(skip_all);

Your script will declare a skip and exit immediately with a zero (success). Test::Harness for details.

Test names

By convention, each test is assigned a number in order. This is largely done automatically for you. However, its often very useful to assign a name to each test. Which would you rather see:

  ok 4
  not ok 5
  ok 6


  ok 4 - basic multi-variable
  not ok 5 - simple exponential
  ok 6 - force == mass * acceleration

The later gives you some idea of what failed. It also makes it easier to find the test in your script, simply search for "simple exponential".

All test functions take a name argument. Its optional, but highly suggested that you use it.

I'm ok, you're not ok.

The basic purpose of this module is to print out either "ok #" or "not ok #" depending on if a given test succeeded or failed. Everything else is just gravy.

All of the following print "ok" or "not ok" depending on if the test succeeded or failed. They all also return true or false, respectively.

  ok($this eq $that, $test_name);

This simply evaluates any expression ($this eq $that is just a simple example) and uses that to determine if the test succeeded or failed. A true expression passes, a false one fails. Very simple.

For example:

    ok( $exp{9} == 81,                   'simple exponential' );
    ok( Film->can('db_Main'),            'set_db()' );
    ok( $p->tests == 4,                  'saw tests' );
    ok( !grep !defined $_, @items,       'items populated' );

(Mnemonic: "This is ok.")

$test_name is a very short description of the test that will be printed out. It makes it very easy to find a test in your script when it fails and gives others an idea of your intentions. $test_name is optional, but we very strongly encourage its use.

Should an ok() fail, it will produce some diagnostics:

    not ok 18 - sufficient mucus
    #     Failed test 18 (foo.t at line 42)

This is actually Test::Simple's ok() routine.

  is  ( $this, $that, $test_name );
  isnt( $this, $that, $test_name );

Similar to ok(), is() and isnt() compare their two arguments with eq and ne respectively and use the result of that to determine if the test succeeded or failed. So these:

    # Is the ultimate answer 42?
    is( ultimate_answer(), 42,          "Meaning of Life" );

    # $foo isn't empty
    isnt( $foo, '',     "Got some foo" );

are similar to these:

    ok( ultimate_answer() eq 42,        "Meaning of Life" );
    ok( $foo ne '',     "Got some foo" );

(Mnemonic: "This is that." "This isn't that.")

So why use these? They produce better diagnostics on failure. ok() cannot know what you are testing for (beyond the name), but is() and isnt() know what the test was and why it failed. For example this test:

    my $foo = 'waffle';  my $bar = 'yarblokos';
    is( $foo, $bar,   'Is foo the same as bar?' );

Will produce something like this:

    not ok 17 - Is foo the same as bar?
    #     Failed test 1 (foo.t at line 139)
    #          got: 'waffle'
    #     expected: 'yarblokos'

So you can figure out what went wrong without rerunning the test.

You are encouraged to use is() and isnt() over ok() where possible, however do not be tempted to use them to find out if something is true or false!

  # XXX BAD!  $pope->isa('Catholic') eq 1
  is( $pope->isa('Catholic'), 1,        'Is the Pope Catholic?' );

This does not check if $pope-isa('Catholic')> is true, it checks if it returns 1. Very different. Similar caveats exist for false and 0. In these cases, use ok().

  ok( $pope->isa('Catholic') ),         'Is the Pope Catholic?' );

For those grammatical pedants out there, there's an isn't() function which is an alias of isnt().

  like( $this, qr/that/, $test_name );

Similar to ok(), like() matches $this against the regex qr/that/.

So this:

    like($this, qr/that/, 'this is like that');

is similar to:

    ok( $this =~ /that/, 'this is like that');

(Mnemonic "This is like that".)

The second argument is a regular expression. It may be given as a regex reference (ie. qr//) or (for better compatibility with older perls) as a string that looks like a regex (alternative delimiters are currently not supported):

    like( $this, '/that/', 'this is like that' );

Regex options may be placed on the end ('/that/i').

Its advantages over ok() are similar to that of is() and isnt(). Better diagnostics on failure.


Sometimes you just want to say that the tests have passed. Usually the case is you've got some complicated condition that is difficult to wedge into an ok(). In this case, you can simply use pass() (to declare the test ok) or fail (for not ok). They are synonyms for ok(1) and ok(0).

Use these very, very, very sparingly.

Module tests

You usually want to test if the module you're testing loads ok, rather than just vomiting if its load fails. For such purposes we have use_ok and require_ok.

   BEGIN { use_ok($module); }

These simply use or require the given $module and test to make sure the load happened ok. Its recommended that you run use_ok() inside a BEGIN block so its functions are exported at compile-time and prototypes are properly honored.

Conditional tests

Sometimes running a test under certain conditions will cause the test script to die. A certain function or method isn't implemented (such as fork() on MacOS), some resource isn't available (like a net connection) or a module isn't available. In these cases its necessary to skip test, or declare that they are supposed to fail but will work in the future (a todo test).

For more details on skip and todo tests, Test::Harness.

  skip BLOCK $how_many, $why, $if;

NOTE Should that be $if or $unless?

This declares a block of tests to skip, why and under what conditions to skip them. An example is the easiest way to illustrate:

    skip {
        ok( head("http://www.foo.com"),     "www.foo.com is alive" );
        ok( head("http://www.foo.com/bar"), "  and has bar" );
    } 2, "LWP::Simple not installed",
    !eval { require LWP::Simple;  LWP::Simple->import;  1 };

The $if condition is optional, but $why is not.

  todo BLOCK $how_many, $why;
  todo BLOCK $how_many, $why, $until;

Declares a block of tests you expect to fail and why. Perhaps its because you haven't fixed a bug:

  todo { is( $Gravitational_Constant, 0 ) }  1,
    "Still tinkering with physics --God";

If you have a set of functionality yet to implement, you can make the whole suite dependent on that new feature.

  todo {
      ok( $pig->altitude > 0 );
      ok( $pig->mach > 2 );
      ok( $pig->serve_peanuts );
  } 1, "Pigs are still safely grounded",

Comparision functions

Not everything is a simple eq check or regex. There are times you need to see if two arrays are equivalent, for instance. For these instances, Test::More provides a handful of useful functions.

NOTE These are NOT well-tested on circular references. Nor am I quite sure what will happen with filehandles.

  eq_array(\@this, \@that);

Checks if two arrays are equivalent. This is a deep check, so multi-level structures are handled correctly.

  eq_hash(\%this, \%that);

Determines if the two hashes contain the same keys and values. This is a deep check.

  eq_set(\@this, \@that);

Similar to eq_array(), except the order of the elements is not important. This is a deep check, but the irrelevancy of order only applies to the top level.


The eq_* family have some caveats.

todo() and skip() are unimplemented.

The no_plan feature depends on new Test::Harness feature. If you're going to distribute tests that use no_plan your end-users will have to upgrade Test::Harness to the latest one on CPAN.


Michael G Schwern <schwern@pobox.com> with much inspiration from Joshua Pritikin's Test module and lots of discussion with Barrie Slaymaker and the perl-qa gang.


This is a case of convergent evolution with Joshua Pritikin's Test module. I was actually largely unware of its existance when I'd first written my own ok() routines. This module exists because I can't figure out how to easily wedge test names into Test's interface (along with a few other problems).

The goal here is to have a testing utility that's simple to learn, quick to use and difficult to trip yourself up with while still providing more flexibility than the existing Test.pm. As such, the names of the most common routines are kept tiny, special cases and magic side-effects are kept to a minimum. WYSIWYG.


Test::Simple if all this confuses you and you just want to write some tests. You can upgrade to Test::More later (its forward compatible).

Test for a similar testing module.

Test::Harness for details on how your test results are interpreted by Perl.

Test::Unit describes a very featureful unit testing interface.

Pod::Tests shows the idea of embedded testing.

SelfTest is another approach to embedded testing.

2 POD Errors

The following errors were encountered while parsing the POD:

Around line 472:

You forgot a '=back' before '=head2'

Around line 536:

You forgot a '=back' before '=head2'