Implementation and test for horizontal rule

src/MdToHTML.hs

@@ -407,9 +407,13 @@ parseOrderedList = do
   void (char '\n') <++ eof
   return $ OrdList (firstLine : lineItems)
 
+parseHorizontalRule :: ReadP MdToken
+parseHorizontalRule = string "---" *> (void (string "\n\n") <++ eof) *> return HorizontalRule
+
 documentParsers :: [ReadP MdToken]
 documentParsers =
-  [ parseHeader,
+  [ parseHorizontalRule,
+    parseHeader,
     parseBlockquote,
     parseUnorderedList,
     parseOrderedList,

src/MdToHtmlTest.hs

@@ -110,6 +110,10 @@ figureTests =
     [ check_equal "Image by itself" "<figure><img src=\"img.png\" alt=\"Image 1\"/><figcaption aria-hidden=\"true\">Image 1</figcaption></figure>" (convert "![Image 1](img.png)")
     ]
 
+horizontalRuleTests =
+  TestList
+    [check_equal "Horizontal Rule" "<p>a</p><hr><p>b</p>" (convert "a\n\n---\n\nb")]
+
 integrationTests =
   TestList
     [ check_equal "Integration 1" "<h1>Sample Markdown</h1><p>This is some basic, sample markdown.</p><h2><b>Second</b> <i>Heading</i></h2>" (convert "# Sample Markdown\n\n This is some basic, sample markdown.\n\n  ## __Second__ _Heading_"),
@@ -147,6 +151,7 @@ tests =
       imageTests,
       figureTests,
       codeTests,
+      horizontalRuleTests,
       integrationTests
     ]