Add binary search tree.

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

@@ -0,0 +1,5 @@
+describe('BinarySearchTree', () => {
+  it('should create binary search tree', () => {
+
+  });
+});

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

@@ -0,0 +1,44 @@
+import BinarySearchTreeNode from '../BinarySearchTreeNode';
+
+describe('BinarySearchTreeNode', () => {
+  it('should create binary search tree', () => {
+    const bstNode = new BinarySearchTreeNode(2);
+
+    expect(bstNode.value).toBe(2);
+    expect(bstNode.left).toBeNull();
+    expect(bstNode.right).toBeNull();
+  });
+
+  it('should insert nodes in correct order', () => {
+    const bstNode = new BinarySearchTreeNode(2);
+    bstNode.insert(1);
+
+    expect(bstNode.toString()).toBe('1,2');
+    expect(bstNode.contains(1)).toBeTruthy();
+    expect(bstNode.contains(3)).toBeFalsy();
+
+    bstNode.insert(3);
+
+    expect(bstNode.toString()).toBe('1,2,3');
+    expect(bstNode.contains(3)).toBeTruthy();
+    expect(bstNode.contains(4)).toBeFalsy();
+
+    bstNode.insert(7);
+
+    expect(bstNode.toString()).toBe('1,2,3,7');
+    expect(bstNode.contains(7)).toBeTruthy();
+    expect(bstNode.contains(8)).toBeFalsy();
+
+    bstNode.insert(4);
+
+    expect(bstNode.toString()).toBe('1,2,3,4,7');
+    expect(bstNode.contains(4)).toBeTruthy();
+    expect(bstNode.contains(8)).toBeFalsy();
+
+    bstNode.insert(6);
+
+    expect(bstNode.toString()).toBe('1,2,3,4,6,7');
+    expect(bstNode.contains(6)).toBeTruthy();
+    expect(bstNode.contains(8)).toBeFalsy();
+  });
+});