diff --git a/src/directory.rs b/src/directory.rs
index 1cfbcc8..5cb2c52 100644
--- a/src/directory.rs
+++ b/src/directory.rs
@@ -158,4 +158,24 @@ mod tests {
             u16::MAX.into()
         );
     }
+
+    #[test]
+    fn iteration_order() {
+        let mut dir = Directory::empty(IfdPointer(0));
+        assert_eq!(dir.len(), 0);
+
+        let fake_entry = Entry::new_u64(crate::tags::Type::BYTE, 0, [0; 8]);
+        dir.extend((0..32).map(|i| {
+            let tag = Tag::Unknown(i);
+            let entry = fake_entry.clone();
+            (tag, entry)
+        }));
+
+        let iter_order: Vec<u16> = dir.iter().map(|(tag, _e)| tag.to_u16()).collect();
+        assert_eq!(
+            iter_order,
+            (0..32).collect::<Vec<_>>(),
+            "Tags must be in ascending order according to the specification"
+        );
+    }
 }
diff --git a/tests/subsubifds.rs b/tests/subsubifds.rs
index 7dfd2ca..3fde959 100644
--- a/tests/subsubifds.rs
+++ b/tests/subsubifds.rs
@@ -29,7 +29,8 @@ fn decode_seek_chain() {
     assert!(!decoder.more_images());
 
     // Ensure we can seek, to do this again.
-    decoder.seek_to_image(0)
+    decoder
+        .seek_to_image(0)
         .expect("Failed to seek to first image");
     assert_eq!(Some(offset0), decoder.ifd_pointer());
     decoder.next_image().unwrap();