test: two setext headings next to each other

Author: ChristianMurphy

Diff for: tests/fuzz.rs

@@ -117,5 +117,13 @@ fn fuzz() -> Result<(), String> {
         "11: gfm task list items followed by eols (GH-24)"
     );
 
+    assert!(
+        matches!(
+            to_mdast("=\n=\n=\na\n=", &Default::default()),
+            Ok(mdast::Node::Root(_))
+        ),
+        "yy: gfm task list items followed by eols (GH-24)"
+    );
+
     Ok(())
 }