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List Archive: gentoo-perl
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To: gentoo-perl@g.o
From: Michael Cummings <mcummings@g.o>
Subject: Re: test
Date: Thu, 07 Sep 2006 13:29:21 -0400
Hash: SHA1

dams wrote:
> test

    Test - provides a simple framework for writing test scripts

      use strict;
      use Test;

      # use a BEGIN block so we print our plan before MyModule is loaded
      BEGIN { plan tests => 14, todo => [3,4] }

      # load your module...
      use MyModule;

      # Helpful notes.  All note-lines must start with a "#".
      print "# I'm testing MyModule version $MyModule::VERSION\n";

      ok(0); # failure
      ok(1); # success

      ok(0); # ok, expected failure (see todo list, above)
      ok(1); # surprise success!

      ok(0,1);             # failure: '0' ne '1'
      ok('broke','fixed'); # failure: 'broke' ne 'fixed'
      ok('fixed','fixed'); # success: 'fixed' eq 'fixed'
      ok('fixed',qr/x/);   # success: 'fixed' =~ qr/x/

      ok(sub { 1+1 }, 2);  # success: '2' eq '2'
      ok(sub { 1+1 }, 3);  # failure: '2' ne '3'

      my @list = (0,0);
      ok @list, 3, "\@list=".join(',',@list);      #extra notes
      ok 'segmentation fault', '/(?i)success/';    #regex match

        $^O =~ m/MSWin/ ? "Skip if MSWin" : 0,  # whether to skip
        $foo, $bar  # arguments just like for ok(...)
        $^O =~ m/MSWin/ ? 0 : "Skip unless MSWin",  # whether to skip
        $foo, $bar  # arguments just like for ok(...)

    This module simplifies the task of writing test files for Perl modules,
    such that their output is in the format that Test::Harness expects to

    To write a test for your new (and probably not even done) module, create
    a new file called t/test.t (in a new t directory). If you have multiple
    test files, to test the "foo", "bar", and "baz" feature sets, then feel
    free to call your files t/foo.t, t/bar.t, and t/baz.t

    This module defines three public functions, "plan(...)", "ok(...)", and
    "skip(...)". By default, all three are exported by the "use Test;"

             BEGIN { plan %theplan; }

        This should be the first thing you call in your test script. It
        declares your testing plan, how many there will be, if any of them
        should be allowed to fail, and so on.

        Typical usage is just:

             use Test;
             BEGIN { plan tests => 23 }

        These are the things that you can put in the parameters to plan:

        "tests => *number*"
            The number of tests in your script. This means all ok() and
            skip() calls.

        "todo => [*1,5,14*]"
            A reference to a list of tests which are allowed to fail. See
            "TODO TESTS".

        "onfail => sub { ... }"
        "onfail => \&some_sub"
            A subroutine reference to be run at the end of the test script,
            if any of the tests fail. See "ONFAIL".

        You must call "plan(...)" once and only once. You should call it in
        a "BEGIN {...}" block, like so:

             BEGIN { plan tests => 23 }

          ok(1 + 1 == 2);
          ok($have, $expect);
          ok($have, $expect, $diagnostics);

        This function is the reason for "Test"'s existence. It's the basic
        function that handles printing ""ok"" or ""not ok"", along with the
        current test number. (That's what "Test::Harness" wants to see.)

        In its most basic usage, "ok(...)" simply takes a single scalar
        expression. If its value is true, the test passes; if false, the
        test fails. Examples:

            # Examples of ok(scalar)

            ok( 1 + 1 == 2 );           # ok if 1 + 1 == 2
            ok( $foo =~ /bar/ );        # ok if $foo contains 'bar'
            ok( baz($x + $y) eq 'Armondo' );    # ok if baz($x + $y) returns
                                                # 'Armondo'
            ok( @a == @b );             # ok if @a and @b are the same

        The expression is evaluated in scalar context. So the following will

            ok( @stuff );                       # ok if @stuff has any
            ok( !grep !defined $_, @stuff );    # ok if everything in
@stuff is
                                                # defined.

        A special case is if the expression is a subroutine reference (in
        either "sub {...}" syntax or "\&foo" syntax). In that case, it is
        executed and its value (true or false) determines if the test passes
        or fails. For example,

            ok( sub {   # See whether sleep works at least passably
              my $start_time = time;
              sleep 5;
              time() - $start_time  >= 4

        In its two-argument form, "ok(*arg1*, *arg2*)" compares the two
        scalar values to see if they match. They match if both are
        undefined, or if *arg2* is a regex that matches *arg1*, or if they
        compare equal with "eq".

            # Example of ok(scalar, scalar)

            ok( "this", "that" );               # not ok, 'this' ne 'that'
            ok( "", undef );                    # not ok, "" is defined

        The second argument is considered a regex if it is either a regex
        object or a string that looks like a regex. Regex objects are
        constructed with the qr// operator in recent versions of perl. A
        string is considered to look like a regex if its first and last
        characters are "/", or if the first character is "m" and its second
        and last characters are both the same non-alphanumeric
        non-whitespace character. These regexp

        Regex examples:

            ok( 'JaffO', '/Jaff/' );    # ok, 'JaffO' =~ /Jaff/
            ok( 'JaffO', 'm|Jaff|' );   # ok, 'JaffO' =~ m|Jaff|
            ok( 'JaffO', qr/Jaff/ );    # ok, 'JaffO' =~ qr/Jaff/;
            ok( 'JaffO', '/(?i)jaff/ ); # ok, 'JaffO' =~ /jaff/i;

        If either (or both!) is a subroutine reference, it is run and used
        as the value for comparing. For example:

            ok sub {
                open(OUT, ">x.dat") || die $!;
                print OUT "\x{e000}";
                close OUT;
                my $bytecount = -s 'x.dat';
                unlink 'x.dat' or warn "Can't unlink : $!";
                return $bytecount;

        The above test passes two values to "ok(arg1, arg2)" -- the first a
        coderef, and the second is the number 4. Before "ok" compares them,
        it calls the coderef, and uses its return value as the real value of
        this parameter. Assuming that $bytecount returns 4, "ok" ends up
        testing "4 eq 4". Since that's true, this test passes.

        Finally, you can append an optional third argument, in
        "ok(*arg1*,*arg2*, *note*)", where *note* is a string value that
        will be printed if the test fails. This should be some useful
        information about the test, pertaining to why it failed, and/or a
        description of the test. For example:

            ok( grep($_ eq 'something unique', @stuff), 1,
                "Something that should be unique isn't!\n".
                '@stuff = '.join ', ', @stuff

        Unfortunately, a note cannot be used with the single argument style
        of "ok()". That is, if you try "ok(*arg1*, *note*)", then "Test"
        will interpret this as "ok(*arg1*, *arg2*)", and probably end up
        testing "*arg1* eq *arg2*" -- and that's not what you want!

        All of the above special cases can occasionally cause some problems.
        See "BUGS and CAVEATS".

    "skip(*skip_if_true*, *args...*)"
        This is used for tests that under some conditions can be skipped.
        It's basically equivalent to:

          if( $skip_if_true ) {
          } else {
            ok( args... );

        ...except that the ok(1) emits not just ""ok *testnum*"" but
        actually ""ok *testnum* # *skip_if_true_value*"".

        The arguments after the *skip_if_true* are what is fed to "ok(...)"
        if this test isn't skipped.

        Example usage:

          my $if_MSWin =
            $^O =~ m/MSWin/ ? 'Skip if under MSWin' : '';

          # A test to be skipped if under MSWin (i.e., run except under
          skip($if_MSWin, thing($foo), thing($bar) );

        Or, going the other way:

          my $unless_MSWin =
            $^O =~ m/MSWin/ ? '' : 'Skip unless under MSWin';

          # A test to be skipped unless under MSWin (i.e., run only
under MSWin)
          skip($unless_MSWin, thing($foo), thing($bar) );

        The tricky thing to remember is that the first parameter is true if
        you want to *skip* the test, not *run* it; and it also doubles as a
        note about why it's being skipped. So in the first codeblock above,
        read the code as "skip if MSWin -- (otherwise) test whether
        "thing($foo)" is "thing($bar)"" or for the second case, "skip unless

        Also, when your *skip_if_reason* string is true, it really should
        (for backwards compatibility with older versions) start with
        the string "Skip", as shown in the above examples.

        Note that in the above cases, "thing($foo)" and "thing($bar)" *are*
        evaluated -- but as long as the "skip_if_true" is true, then we
        "skip(...)" just tosses out their value (i.e., not bothering to
        treat them like values to "ok(...)". But if you need to *not* eval
        the arguments when skipping the test, use this format:

          skip( $unless_MSWin,
            sub {
              # This code returns true if the test passes.
              # (But it doesn't even get called if the test is skipped.)
              thing($foo) eq thing($bar)

        or even this, which is basically equivalent:

          skip( $unless_MSWin,
            sub { thing($foo) }, sub { thing($bar) }

        That is, both are like this:

          if( $unless_MSWin ) {
            ok(1);  # but it actually appends "# $unless_MSWin"
                    #  so that Test::Harness can tell it's a skip
          } else {
            # Not skipping, so actually call and evaluate...
            ok( sub { thing($foo) }, sub { thing($bar) } );

        These tests are expected to succeed. Usually, most or all of your
        tests are in this category. If a normal test doesn't succeed, then
        that means that something is *wrong*.

        The "skip(...)" function is for tests that might or might not be
        possible to run, depending on the availability of platform-specific
        features. The first argument should evaluate to true (think "yes,
        please skip") if the required feature is *not* available. After the
        first argument, "skip(...)" works exactly the same way as "ok(...)"

        TODO tests are designed for maintaining an executable TODO list.
        These tests are *expected to fail.* If a TODO test does succeed,
        then the feature in question shouldn't be on the TODO list, now
        should it?

        Packages should NOT be released with succeeding TODO tests. As soon
        as a TODO test starts working, it should be promoted to a normal
        test, and the newly working feature should be documented in the
        release notes or in the change log.

      BEGIN { plan test => 4, onfail => sub { warn "CALL 911!" } }

    Although test failures should be enough, extra diagnostics can be
    triggered at the end of a test run. "onfail" is passed an array ref of
    hash refs that describe each test failure. Each hash will contain at
    least the following fields: "package", "repetition", and "result". (You
    shouldn't rely on any other fields being present.) If the test had an
    expected value or a diagnostic (or "note") string, these will also be

    The *optional* "onfail" hook might be used simply to print out the
    version of your package and/or how to report problems. It might also be
    used to generate extremely sophisticated diagnostics for a particularly
    bizarre test failure. However it's not a panacea. Core dumps or other
    unrecoverable errors prevent the "onfail" hook from running. (It is run
    inside an "END" block.) Besides, "onfail" is probably over-kill in most
    cases. (Your test code should be simpler than the code it is testing,

    *   "ok(...)"'s special handing of strings which look like they might be
        regexes can also cause unexpected behavior. An innocent:

            ok( $fileglob, '/path/to/some/*stuff/' );

        will fail, since considers the second argument to be a
        regex! The best bet is to use the one-argument form:

            ok( $fileglob eq '/path/to/some/*stuff/' );

    *   "ok(...)"'s use of string "eq" can sometimes cause odd problems when
        comparing numbers, especially if you're casting a string to a

            $foo = "1.0";
            ok( $foo, 1 );      # not ok, "1.0" ne 1

        Your best bet is to use the single argument form:

            ok( $foo == 1 );    # ok "1.0" == 1

    *   As you may have inferred from the above documentation and examples,
        "ok"'s prototype is "($;$$)" (and, incidentally, "skip"'s is
        "($;$$$)"). This means, for example, that you can do "ok @foo, @bar"
        to compare the *size* of the two arrays. But don't be fooled into
        thinking that "ok @foo, @bar" means a comparison of the contents of
        two arrays -- you're comparing *just* the number of elements of
        each. It's so easy to make that mistake in reading "ok @foo, @bar"
        that you might want to be very explicit about it, and instead write
        "ok scalar(@foo), scalar(@bar)".

    *   This almost definitely doesn't do what you expect:

             ok $thingy->can('some_method');

        Why? Because "can" returns a coderef to mean "yes it can (and the
        method is this...)", and then "ok" sees a coderef and thinks you're
        passing a function that you want it to call and consider the truth
        of the result of! I.e., just like:

             ok $thingy->can('some_method')->();

        What you probably want instead is this:

             ok $thingy->can('some_method') && 1;

        If the "can" returns false, then that is passed to "ok". If it
        returns true, then the larger expression
        "$thingy->can('some_method') && 1" returns 1, which "ok" sees as a
        simple signal of success, as you would expect.

    *   The syntax for "skip" is about the only way it can be, but it's
        still quite confusing. Just start with the above examples and you'll
        be okay.

        Moreover, users may expect this:

          skip $unless_mswin, foo($bar), baz($quux);

        to not evaluate "foo($bar)" and "baz($quux)" when the test is being
        skipped. But in reality, they *are* evaluated, but "skip" just won't
        bother comparing them if $unless_mswin is true.

        You could do this:

          skip $unless_mswin, sub{foo($bar)}, sub{baz($quux)};

        But that's not terribly pretty. You may find it simpler or clearer
        in the long run to just do things like this:

          if( $^O =~ m/MSWin/ ) {
            print "# Yay, we're under $^O\n";
            ok foo($bar), baz($quux);
            ok thing($whatever), baz($stuff);
            ok blorp($quux, $whatever);
            ok foo($barzbarz), thang($quux);
          } else {
            print "# Feh, we're under $^O.  Watch me skip some tests...\n";
            for(1 .. 4) { skip "Skip unless under MSWin" }

        But be quite sure that "ok" is called exactly as many times in the
        first block as "skip" is called in the second block.

    If "PERL_TEST_DIFF" environment variable is set, it will be used as a
    command for comparing unexpected multiline results. If you have GNU diff
    installed, you might want to set "PERL_TEST_DIFF" to "diff -u". If you
    don't have a suitable program, you might install the "Text::Diff" module
    and then set "PERL_TEST_DIFF" to be "perl -MText::Diff -e 'print
    diff(@ARGV)'". If "PERL_TEST_DIFF" isn't set but the "Algorithm::Diff"
    module is available, then it will be used to show the differences in
    multiline results.

    A past developer of this module once said that it was no longer being
    actively developed. However, rumors of its demise were greatly
    exaggerated. Feedback and suggestions are quite welcome.

    Be aware that the main value of this module is its simplicity. Note that
    there are already more ambitious modules out there, such as Test::More
    and Test::Unit.

    Some earlier versions of this module had docs with some confusing typoes
    in the description of "skip(...)".


    Test::Simple, Test::More, Devel::Cover

    Test::Builder for building your own testing library.

    Test::Unit is an interesting XUnit-style testing library.

    Test::Inline and SelfTest let you embed tests in code.

    Copyright (c) 1998-2000 Joshua Nathaniel Pritikin. All rights reserved.

    Copyright (c) 2001-2002 Michael G. Schwern.

    Copyright (c) 2002-2004 and counting Sean M. Burke.

    Current maintainer: Sean M. Burke. <sburke@...>

    This package is free software and is provided "as is" without express or
    implied warranty. It may be used, redistributed and/or modified under
    the same terms as Perl itself.

- --

- -----o()o----------------------------------------------
Michael Cummings   |    #gentoo-dev, #gentoo-perl
Gentoo Perl Dev    |    on
GPG: 0543 6FA3 5F82 3A76 3BF7  8323 AB5C ED4E 9E7F 4E2E
- -----o()o----------------------------------------------
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gentoo-perl@g.o mailing list

Re: test
-- Chris White
-- dams
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Updated Jun 17, 2009

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