diff --git a/crates/rle/src/rle_tree/test/mod.rs b/crates/rle/src/rle_tree/test/mod.rs
index fe07eb57..2e34f024 100644
--- a/crates/rle/src/rle_tree/test/mod.rs
+++ b/crates/rle/src/rle_tree/test/mod.rs
@@ -1 +1,2 @@
 mod range_rle_test;
+mod string_fuzzy;
diff --git a/crates/rle/src/rle_tree/test/string_fuzzy.rs b/crates/rle/src/rle_tree/test/string_fuzzy.rs
new file mode 100644
index 00000000..8545d74d
--- /dev/null
+++ b/crates/rle/src/rle_tree/test/string_fuzzy.rs
@@ -0,0 +1,93 @@
+use std::ops::{Deref, DerefMut};
+
+use crate::{rle_tree::tree_trait::RleTreeTrait, HasLength, Mergable, Sliceable};
+
+#[derive(Debug)]
+struct CustomString(String);
+impl Deref for CustomString {
+    type Target = String;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for CustomString {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl HasLength for CustomString {
+    fn len(&self) -> usize {
+        self.0.len()
+    }
+}
+
+impl Mergable for CustomString {
+    fn is_mergable(&self, other: &Self, _conf: &()) -> bool
+    where
+        Self: Sized,
+    {
+        self.len() + other.len() < 16
+    }
+
+    fn merge(&mut self, other: &Self, _conf: &())
+    where
+        Self: Sized,
+    {
+        self.push_str(other.as_str())
+    }
+}
+
+impl Sliceable for CustomString {
+    fn slice(&self, from: usize, to: usize) -> Self {
+        CustomString(self.0.slice(from, to))
+    }
+}
+
+#[derive(Debug)]
+struct StringTreeTrait;
+impl RleTreeTrait<CustomString> for StringTreeTrait {
+    const MAX_CHILDREN_NUM: usize = 4;
+
+    const MIN_CHILDREN_NUM: usize = Self::MAX_CHILDREN_NUM / 2;
+
+    type Int = usize;
+
+    type InternalCache = usize;
+
+    type LeafCache = usize;
+
+    fn update_cache_leaf(node: &mut crate::rle_tree::node::LeafNode<'_, CustomString, Self>) {
+        todo!()
+    }
+
+    fn update_cache_internal(
+        node: &mut crate::rle_tree::node::InternalNode<'_, CustomString, Self>,
+    ) {
+        todo!()
+    }
+
+    fn find_pos_internal(
+        node: &mut crate::rle_tree::node::InternalNode<'_, CustomString, Self>,
+        index: Self::Int,
+    ) -> (usize, Self::Int, crate::rle_tree::tree_trait::Position) {
+        todo!()
+    }
+
+    fn find_pos_leaf(
+        node: &mut crate::rle_tree::node::LeafNode<'_, CustomString, Self>,
+        index: Self::Int,
+    ) -> (usize, usize, crate::rle_tree::tree_trait::Position) {
+        todo!()
+    }
+
+    fn len_leaf(node: &crate::rle_tree::node::LeafNode<'_, CustomString, Self>) -> usize {
+        todo!()
+    }
+
+    fn len_internal(node: &crate::rle_tree::node::InternalNode<'_, CustomString, Self>) -> usize {
+        todo!()
+    }
+}