Test::LongString(3) User Contributed Perl Documentation Test::LongString(3)

# [NAME](#NAME)

Test::LongString - tests strings for equality, with more helpful failures

# [SYNOPSIS](#SYNOPSIS)

```
    use Test::More tests => 1;
    use Test::LongString;
    like_string( $html, qr/(perl|cpan)\.org/ );
    #     Failed test (html-test.t at line 12)
    #          got: "<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Trans"...
    #       length: 58930
    #     doesn't match '(?-xism:(perl|cpan)\.org)'
```

# [DESCRIPTION](#DESCRIPTION)

This module provides some drop-in replacements for the string comparison functions of Test::More, but which are more suitable when you test against long strings. If you've ever had to search for text in a multi-line string like an HTML document, or find specific items in binary data, this is the module for you.

# [FUNCTIONS](#FUNCTIONS)

## [is\_string( $string, $expected \[, $label \] )](#is_string%28_$string,_$expected__,_$label___%29)

is\_string() is equivalent to Test::More::is(), but with more helpful diagnostics in case of failure.

- It doesn't print the entire strings in the failure message.
- It reports the lengths of the strings that have been compared.
- It reports the length of the common prefix of the strings.
- It reports the line and column the strings started to differ on.
- In the diagnostics, non-ASCII characters are escaped as "\\x{xx}".

For example:

```
    is_string( $soliloquy, $juliet );
    #     Failed test (soliloquy.t at line 15)
    #          got: "To be, or not to be: that is the question:\x{0a}Whether"...
    #       length: 1490
    #     expected: "O Romeo, Romeo,\x{0a}wherefore art thou Romeo?\x{0a}Deny thy"...
    #       length: 154
    #     strings begin to differ at char 1 (line 1 column 1)
```

## [is\_string\_nows( $string, $expected \[, $label \] )](#is_string_nows%28_$string,_$expected__,_$label___%29)

Like is\_string(), but removes whitespace (in the "\\s" sense) from the arguments before comparing them.

## [like\_string( $string, qr/regex/ \[, $label \] )](#like_string%28_$string,_qr/regex/__,_$label___%29)

## [unlike\_string( $string, qr/regex/ \[, $label \] )](#unlike_string%28_$string,_qr/regex/__,_$label___%29)

like\_string() and unlike\_string() are replacements for Test::More:like() and unlike() that only print the beginning of the received string in the output. Unfortunately, they can't print out the position where the regex failed to match.

```
    like_string( $soliloquy, qr/Romeo|Juliet|Mercutio|Tybalt/ );
    #     Failed test (soliloquy.t at line 15)
    #          got: "To be, or not to be: that is the question:\x{0a}Whether"...
    #       length: 1490
    #     doesn't match '(?-xism:Romeo|Juliet|Mercutio|Tybalt)'
```

## [contains\_string( $string, $substring \[, $label \] )](#contains_string%28_$string,_$substring__,_$label___%29)

contains\_string() searches for *$substring* in *$string*. It's the same as like\_string(), except that it's not a regular expression search.

```
    contains_string( $soliloquy, "Romeo" );
    #     Failed test (soliloquy.t at line 10)
    #         searched: "To be, or not to be: that is the question:\x{0a}Whether"...
    #   and can't find: "Romeo"
```

As of version 0.12, contains\_string() will also report the Longest Common SubString (LCSS) found in *$string* and, if the LCSS is short enough, the surroundings will also be shown under *LCSS Context*. This should help debug tests for really long strings like HTML output, so you'll get something like:

```
   contains_string( $html, '<div id="MainContent">' );
   #   Failed test at t/foo.t line 10.
   #     searched: "<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Stric"...
   #   can't find: "<div id="MainContent">"
   #         LCSS: "ainContent""
   # LCSS context: "dolor sit amet</span>\x{0a}<div id="mainContent" class="
```

You can turn off LCSS reporting by setting $Test::LongString::LCSS to 0, or by specifying an argument to "use":

```
    use Test::LongString lcss => 0;
```

## [lacks\_string( $string, $substring \[, $label \] )](#lacks_string%28_$string,_$substring__,_$label___%29)

lacks\_string() makes sure that *$substring* does NOT exist in *$string*. It's the same as like\_string(), except that it's not a regular expression search.

```
    lacks_string( $soliloquy, "slings" );
    #     Failed test (soliloquy.t at line 10)
    #         searched: "To be, or not to be: that is the question:\x{0a}Whether"...
    #        and found: "slings"
    #      at position: 147 (line 3 column 4)
```

# [CONTROLLING OUTPUT](#CONTROLLING_OUTPUT)

By default, only the first 50 characters of the compared strings are shown in the failure message. This value is in $Test::LongString::Max, and can be set at run-time.

You can also set it by specifying an argument to "use":

```
    use Test::LongString max => 100;
```

When the compared strings begin to differ after a large prefix, Test::LongString will not print them from the beginning, but will start at the middle, more precisely at $Test::LongString::Context characters before the first difference. By default this value is 10 characters. If you want Test::LongString to always print the beginning of compared strings no matter where they differ, undefine $Test::LongString::Context.

When computing line numbers this module uses "\\n" to count line endings. This may not be appropriate for strings on your platform, and can be overridden by setting the $Test::LongString::EOL variable to a suitable regular expression (either a reference to a regular expression or a string that can be interpolated into a regular expression.)

You can also set it by specifying an argument to "use":

```
    use Test::LongString eol => "\x{0a}\x{0c}";
```

# [AUTHOR](#AUTHOR)

Written by Rafael Garcia-Suarez. Thanks to Mark Fowler (and to Joss Whedon) for the inspirational Acme::Test::Buffy. Thanks to Andy Lester for lots of patches.

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

A git repository for this module is available at

```
    git://github.com/rgs/Test-LongString.git
```

and the project page at

```
    http://github.com/rgs/Test-LongString
```

# [SEE ALSO](#SEE_ALSO)

Test::Builder, Test::Builder::Tester, Test::More.

2026-09-28 perl v5.44.0

---

Document: Test::LongString(3pm) from perl-test-longstring 0.17-r2 (Chainguard OS)
Source: https://cpan.metacpan.org/authors/id/R/RG/RGARCIA/Test-LongString-0.17.tar.gz