Add test

diff --git a/tests/test_port/fixtures/issue-fixes.md b/tests/test_port/fixtures/issue-fixes.md
index 5ff0973..61d7029 100644
--- a/tests/test_port/fixtures/issue-fixes.md
+++ b/tests/test_port/fixtures/issue-fixes.md

@@ -13,3 +13,12 @@
 <li>b</li>
 </ul>
 .
+
+#50 literal in block raise `IndexError`:
+.
+> `!conda install quantecon`
+.
+<blockquote>
+<p><code>!conda install quantecon</code></p>
+</blockquote>
+.