test: add regression test

lib/MarkdownParser.pm

@@ -10,6 +10,7 @@ my %CLOSING_TAGS = (
     olist      => "</ol>",
     blockquote => "</blockquote>",
     table      => "</table>",
+    code_block => "</code></pre>",
 );
 
 sub new {
@@ -166,7 +167,6 @@ sub handle_code_block_line {
     my ( $self, $line ) = @_;
 
     if ( $line =~ /^```/ ) {
-        $self->{output} .= "</code></pre>\n";
         $self->transition_to_state('paragraph');
     }
     else {

t/06-code.t

@@ -2,7 +2,7 @@
 use strict;
 use warnings;
 
-use Test::More tests => 5;
+use Test::More tests => 6;
 use MarkdownParser;
 
 my $parser = MarkdownParser->new();
@@ -32,4 +32,8 @@ is(
     "<pre><code>\n</code></pre>\n",
     "Empty code block"
 );
-
+is(
+    $parser->parse("```\nunterminated"),
+    "<pre><code>\nunterminated\n</code></pre>\n",
+    "Unclosed code block is closed at EOF"
+);