Fix HTTP links in URI docs.

tests/utils/src/MarkdownTest.dart

Index: tests/utils/src/MarkdownTest.dart
diff --git a/tests/utils/src/MarkdownTest.dart b/tests/utils/src/MarkdownTest.dart
index b3cd0a5b91f314680adbf3f472ab66001054c97e..50a41a70387a2135a7323c6853645688cab555ff 100644
--- a/tests/utils/src/MarkdownTest.dart
+++ b/tests/utils/src/MarkdownTest.dart
@@ -707,6 +707,20 @@ void main() {
         ''', '''
         <p>[bad] <code>code</code></p>
         ''');
+    validate('empty reference uses text from link', '''
+        links [are][] awesome
+
+        [are]: http://foo.com
+        ''', '''
+        <p>links <a href="http://foo.com">are</a> awesome</p>
+        ''');
+    validate('references are case-insensitive', '''
+        links [ARE][] awesome
+
+        [are]: http://foo.com
+        ''', '''
+        <p>links <a href="http://foo.com">ARE</a> awesome</p>
+        ''');
   });
 
   group('Inline links', () {