Add test

src/operation_transformation/utils/elongate_operations.rs

@@ -19,7 +19,6 @@ where
 
     // We don't elongate `equals` as they're needed to maintain cursor positions
     // when merging against deletes.
-
     let mut result: Vec<RawOperation<T>> = raw_operations
         .into_iter()
         .flat_map(|next| match next {
@@ -63,3 +62,61 @@ where
 
     result
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::tokenizer::token::Token;
+
+    // Helper constructors for cleaner tests
+    fn ins(texts: &[&str]) -> RawOperation<String> {
+        RawOperation::Insert(texts.iter().map(|t| Token::from(*t)).collect())
+    }
+
+    fn del(texts: &[&str]) -> RawOperation<String> {
+        RawOperation::Delete(texts.iter().map(|t| Token::from(*t)).collect())
+    }
+
+    fn ins_custom(text: &str, lj: bool, rj: bool) -> RawOperation<String> {
+        RawOperation::Insert(vec![Token::new(text.to_string(), text.to_string(), lj, rj)])
+    }
+
+    #[test]
+    fn merges_adjacent_joinable_inserts() {
+        let ops = vec![ins(&["a"]), ins(&["b"]), ins(&["c"])];
+        let result = elongate_operations(ops);
+        assert_eq!(result.len(), 1);
+        match &result[0] {
+            RawOperation::Insert(tokens) => {
+                let originals: String = tokens.iter().map(|t| t.original()).collect();
+                assert_eq!(originals, "abc");
+            }
+            _ => panic!("Expected single Insert operation"),
+        }
+    }
+
+    #[test]
+    fn does_not_merge_when_not_joinable() {
+        let ops = vec![
+            ins_custom("a", true, false), // not right-joinable
+            ins_custom("b", true, true),  // left-joinable but previous isn't right-joinable
+        ];
+        let result = elongate_operations(ops);
+        assert_eq!(
+            result.len(),
+            2,
+            "Operations should remain separate when not joinable"
+        );
+    }
+
+    #[test]
+    fn merges_interleaved_insert_delete_sequences() {
+        // Pattern IDID -> II DD
+        let ops = vec![ins(&["i1"]), del(&["d1"]), ins(&["i2"]), del(&["d2"])];
+        let result = elongate_operations(ops);
+
+        assert_eq!(result.len(), 2);
+        assert!(matches!(result[0], RawOperation::Delete(_)));
+        assert!(matches!(result[1], RawOperation::Insert(_)));
+    }
+}