Because you won't know if your test suite crashes right in the middle: 
use Test::More qw(no_plan);
ok(1);
   # CRASH!!
exit(0);
ok(2);

[download]
If you run that with the harness as in PERL_DL_NONLAZY=1 perl "-MExtUtils::Command::MM" "-e" "test_harness(0, 'blib/lib', 'blib/arch')" test.pl it will happily report 
All tests successful.
Files=1, Tests=1

[download]
because it doesn't know better. If you had specified the desired outcome, as in 
use Test::More tests => 2;

[download]
the test script would have reported 
# Looks like you planned 2 tests but only ran 1.

[download]
and the harness would have failed, allowing you to catch the bug while it goes unnoticed otherwise.

In reply to Re: No plan "weakens" my Test scripts? by saintmike
in thread No plan "weakens" my Test scripts? by thor

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.