improve tests

Parsedown.php

@@ -438,6 +438,11 @@ class Parsedown
                         $substring = substr($outdented_line, $position + 2);
                         $substring = trim($substring);
 
+                        if ($substring === '')
+                        {
+                            break;
+                        }
+
                         if ($substring[0] === '<')
                         {
                             $position = strpos($substring, '>');
@@ -471,22 +476,19 @@ class Parsedown
 
                         if ($substring !== false)
                         {
+                            if ($substring[0] !== '"' and $substring[0] !== "'" and $substring[0] !== '(')
+                            {
+                                break;
+                            }
+
                             $last_char = substr($substring, -1);
 
-                            switch (true)
+                            if ($last_char !== '"' and $last_char !== "'" and $last_char !== ')')
                             {
-                                case $substring[0] === '"' and $substring[0] === $last_char:
-                                case $substring[0] === "'" and $substring[0] === $last_char:
-                                case $substring[0] === '(' and $last_char === ')':
-
-                                    $reference['#'] = substr($substring, 1, -1);
-
-                                    break;
-
-                                default:
-
-                                    break 2;
+                                break;
                             }
+
+                            $reference['#'] = substr($substring, 1, -1);
                         }
 
                         $this->reference_map[$label] = $reference;

tests/data/inline_link_title.html

@@ -0,0 +1 @@
+<p><a href="http://example.com" title="Title">single quotes</a> and <a href="http://example.com" title="Title">double quotes</a></p>

tests/data/inline_link_title.md

@@ -0,0 +1 @@
+[single quotes](http://example.com 'Title') and [double quotes](http://example.com "Title")

tests/data/reference_title.html

@@ -1 +1,2 @@
-<p><a href="http://example.com" title="Title">single quotes</a> and <a href="http://example.com" title="Title">double quotes</a></p>
+<p><a href="http://example.com" title="example title">double quotes</a> and <a href="http://example.com" title="example title">single quotes</a> and <a href="http://example.com" title="example title">parentheses</a></p>
+<p>[invalid title]: <a href="http://example.com">http://example.com</a> example title</p>

tests/data/reference_title.md

@@ -1 +1,6 @@
-[single quotes](http://example.com 'Title') and [double quotes](http://example.com "Title")
+[double quotes] and [single quotes] and [parentheses]
+
+[double quotes]: http://example.com "example title"
+[single quotes]: http://example.com 'example title'
+[parentheses]: http://example.com (example title)
+[invalid title]: http://example.com example title