NAME

       Test::utf8 - handy utf8 tests

SYNOPSIS

         # check the string is good
         is_valid_string($string);   # check the string is valid
         is_sane_utf8($string);      # check not double encoded

         # check the string has certain attributes
         is_flagged_utf8($string1);   # has utf8 flag set
         is_within_ascii($string2);   # only has ascii chars in it
         isnt_within_ascii($string3); # has chars outside the ascii range
         is_within_latin_1($string4); # only has latin-1 chars in it
         isnt_within_ascii($string5); # has chars outside the latin-1 range

DESCRIPTION

       This module is a collection of tests useful for dealing with utf8 strings in Perl.

       This module has two types of tests: The validity tests check if a string is valid and not
       corrupt, whereas the characteristics tests will check that string has a given set of
       characteristics.

   Validity Tests
       is_valid_string($string, $testname)
           Checks if the string is "valid", i.e. this passes and returns true unless the internal
           utf8 flag hasn't been set on scalar that isn't made up of a valid utf-8 byte sequence.

           This should never happen and, in theory, this test should always pass. Unless you (or
           a module you use) goes monkeying around inside a scalar using Encode's private
           functions or XS code you shouldn't ever end up in a situation where you've got a
           corrupt scalar.  But if you do, and you do, then this function should help you detect
           the problem.

           To be clear, here's an example of the error case this can detect:

             my $mark = "Mark";
             my $leon = "L\x{e9}on";
             is_valid_string($mark);  # passes, not utf-8
             is_valid_string($leon);  # passes, not utf-8

             my $iloveny = "I \x{2665} NY";
             is_valid_string($iloveny);      # passes, proper utf-8

             my $acme = "L\x{c3}\x{a9}on";
             Encode::_utf8_on($acme);      # (please don't do things like this)
             is_valid_string($acme);       # passes, proper utf-8 byte sequence upgraded

             Encode::_utf8_on($leon);      # (this is why you don't do things like this)
             is_valid_string($leon);       # fails! the byte \x{e9} isn't valid utf-8

       is_sane_utf8($string, $name)
           This test fails if the string contains something that looks like it might be dodgy
           utf8, i.e. containing something that looks like the multi-byte sequence for a latin-1
           character but perl hasn't been instructed to treat as such.  Strings that are not utf8
           always automatically pass.

           Some examples may help:

             # This will pass as it's a normal latin-1 string
             is_sane_utf8("Hello L\x{e9}eon");

             # this will fail because the \x{c3}\x{a9} looks like the
             # utf8 byte sequence for e-acute
             my $string = "Hello L\x{c3}\x{a9}on";
             is_sane_utf8($string);

             # this will pass because the utf8 is correctly interpreted as utf8
             Encode::_utf8_on($string)
             is_sane_utf8($string);

           Obviously this isn't a hundred percent reliable.  The edge case where this will fail
           is where you have "\x{c2}" (which is "LATIN CAPITAL LETTER WITH CIRCUMFLEX") or
           "\x{c3}" (which is "LATIN CAPITAL LETTER WITH TILDE") followed by one of the latin-1
           punctuation symbols.

             # a capital letter A with tilde surrounded by smart quotes
             # this will fail because it'll see the "\x{c2}\x{94}" and think
             # it's actually the utf8 sequence for the end smart quote
             is_sane_utf8("\x{93}\x{c2}\x{94}");

           However, since this hardly comes up this test is reasonably reliable in most cases.
           Still, care should be applied in cases where dynamic data is placed next to latin-1
           punctuation to avoid false negatives.

           There exists two situations to cause this test to fail; The string contains utf8 byte
           sequences and the string hasn't been flagged as utf8 (this normally means that you got
           it from an external source like a C library; When Perl needs to store a string
           internally as utf8 it does it's own encoding and flagging transparently) or a utf8
           flagged string contains byte sequences that when translated to characters themselves
           look like a utf8 byte sequence.  The test diagnostics tells you which is the case.

   String Characteristic Tests
       These routines allow you to check the range of characters in a string.  Note that these
       routines are blind to the actual encoding perl internally uses to store the characters,
       they just check if the string contains only characters that can be represented in the
       named encoding:

       is_within_ascii
           Tests that a string only contains characters that are in the ASCII charecter set.

       is_within_latin_1
           Tests that a string only contains characters that are in latin-1.

       Simply check if a scalar is or isn't flagged as utf8 by perl's internals:

       is_flagged_utf8($string, $name)
           Passes if the string is flagged by perl's internals as utf8, fails if it's not.

       isnt_flagged_utf8($string,$name)
           The opposite of "is_flagged_utf8", passes if and only if the string isn't flagged as
           utf8 by perl's internals.

           Note: you can refer to this function as "isn't_flagged_utf8" if you really want to.

AUTHOR

       Written by Mark Fowler mark@twoshortplanks.com

COPYRIGHT

       Copyright Mark Fowler 2004,2012.  All rights reserved.

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

BUGS

       None known.  Please report any to me via the CPAN RT system.  See http://rt.cpan.org/ for
       more details.

SEE ALSO

       Test::DoubleEncodedEntities for testing for double encoded HTML entities.