diff --git a/src/data-structures/binary-tree/rb-tree.ts b/src/data-structures/binary-tree/rb-tree.ts
index 9009419..e72b88a 100644
--- a/src/data-structures/binary-tree/rb-tree.ts
+++ b/src/data-structures/binary-tree/rb-tree.ts
@@ -140,7 +140,7 @@ export class RedBlackTree {
         y.color = z.color;
       }
       if (yOriginalColor === 0) {
-        this.fixDelete(x);
+        this._fixDelete(x);
       }
     }
     helper(this.root);
@@ -170,7 +170,7 @@ export class RedBlackTree {
     return dfs(beginRoot);
   }
 
- 
+
   /**
    * The function returns the leftmost node in a red-black tree.
    * @param {RBTreeNode} node - The parameter "node" is of type RBTreeNode, which represents a node in
@@ -283,11 +283,11 @@ export class RedBlackTree {
   }
 
   /**
-   * The fixDelete function is used to rebalance the Red-Black Tree after a node deletion.
+   * The _fixDelete function is used to rebalance the Red-Black Tree after a node deletion.
    * @param {RBTreeNode} x - The parameter `x` is of type `RBTreeNode`, which represents a node in a
    * red-black tree.
    */
-  protected fixDelete(x: RBTreeNode): void {
+  protected _fixDelete(x: RBTreeNode): void {
     let s: RBTreeNode;
     while (x !== this.root && x.color === 0) {
       if (x === x.parent.left) {
diff --git a/test/unit/data-structures/binary-tree/rb-tree.test.ts b/test/unit/data-structures/binary-tree/rb-tree.test.ts
index fd76114..37b8643 100644
--- a/test/unit/data-structures/binary-tree/rb-tree.test.ts
+++ b/test/unit/data-structures/binary-tree/rb-tree.test.ts
@@ -1,4 +1,5 @@
 import { RedBlackTree, RBTreeNode } from '../../../../src';
+import {getRandomInt} from "../../../utils";
 
 describe('RedBlackTree', () => {
   let tree: RedBlackTree;
@@ -134,3 +135,108 @@ describe('RedBlackTree', () => {
     });
   });
 });
+
+
+describe('RedBlackTree', () => {
+  let tree: RedBlackTree;
+
+  beforeEach(() => {
+    tree = new RedBlackTree();
+  });
+
+  it('should insert nodes into the tree', () => {
+    tree.insert(10);
+    expect(tree.getNode(10)).toBeDefined();
+    tree.insert(20);
+    expect(tree.getNode(20)).toBeDefined();
+    tree.insert(5);
+    expect(tree.getNode(5)).toBeDefined();
+  });
+
+  it('should delete nodes from the tree', () => {
+    tree.insert(10);
+    tree.insert(20);
+    tree.insert(5);
+    tree.delete(20);
+    expect(tree.getNode(20)).toBe(tree.NIL);
+  });
+
+  it('should get the successor of a node', () => {
+    tree.insert(10);
+    tree.insert(20);
+    const node = tree.getNode(10);
+    const successor = tree.getSuccessor(node);
+    expect(successor?.key).toBe(20);
+  });
+
+  it('should get the predecessor of a node', () => {
+    tree.insert(10);
+    tree.insert(20);
+    const node = tree.getNode(20);
+    const predecessor = tree.getPredecessor(node);
+    expect(predecessor?.key).toBe(10);
+  });
+
+  it('should rotate nodes to the left', () => {
+    tree.insert(10);
+    tree.insert(20);
+    tree.insert(5);
+    const node = tree.getNode(10);
+    tree.insert(15);
+    // Verify that rotation has occurred
+    expect(node.left.key).toBe(5);
+    expect(node.right.key).toBe(20);
+  });
+
+  it('should rotate nodes to the right', () => {
+    tree.insert(10);
+    tree.insert(20);
+    tree.insert(5);
+    const node = tree.getNode(20);
+    tree.insert(25);
+    // Verify that rotation has occurred
+    expect(node.left.key).toBe(0);
+    expect(node.right.key).toBe(25);
+  });
+
+  it('should fix the tree after deletion', () => {
+    tree.insert(10);
+    tree.insert(20);
+    tree.insert(5);
+    tree.insert(15);
+    tree.delete(15);
+    // Verify that the tree is still valid
+    // You can add assertions to check the Red-Black Tree properties
+  });
+
+  it('should fix the tree after insertion', () => {
+    for (let i = 0; i < 1000; i++) {
+      tree.insert(getRandomInt(-100, 1000));
+      tree.delete(getRandomInt(-100, 1000));
+    }
+    tree.insert(1);
+    tree.insert(2);
+    tree.insert(5);
+    tree.insert(15);
+    tree.insert(25);
+    tree.insert(10);
+    tree.insert(8);
+    tree.insert(28);
+    tree.insert(111);
+    tree.insert(12);
+    tree.delete(2);
+    tree.insert(22);
+    tree.insert(50);
+    tree.insert(155);
+    tree.insert(225);
+    tree.insert(7);
+    tree.delete(15);
+    tree.insert(23);
+    tree.insert(33);
+    tree.insert(15);
+
+
+    // Verify that the tree is still a valid Red-Black Tree
+    // You can add assertions to check the Red-Black Tree properties
+  });
+});