Add binary search tree.

src/data-structures/tree/binary-search-tree/__test__/BinarySearchTree.test.js

@@ -1,5 +1,34 @@
+import BinarySearchTree from '../BinarySearchTree';
+
 describe('BinarySearchTree', () => {
   it('should create binary search tree', () => {
+    const bst = new BinarySearchTree();
 
+    expect(bst).toBeDefined();
+    expect(bst.root).toBeDefined();
+    expect(bst.root.value).toBeNull();
+    expect(bst.root.left).toBeNull();
+    expect(bst.root.right).toBeNull();
+  });
+
+  it('should insert values', () => {
+    const bst = new BinarySearchTree();
+
+    bst.insert(10);
+    bst.insert(20);
+    bst.insert(5);
+
+    expect(bst.toString()).toBe('5,10,20');
+  });
+
+  it('should check if value exists', () => {
+    const bst = new BinarySearchTree();
+
+    bst.insert(10);
+    bst.insert(20);
+    bst.insert(5);
+
+    expect(bst.contains(20)).toBeTruthy();
+    expect(bst.contains(40)).toBeFalsy();
   });
 });