diff --git a/JavaScript/4-functional.js b/JavaScript/4-functional.js
index b09b054..9dec73e 100644
--- a/JavaScript/4-functional.js
+++ b/JavaScript/4-functional.js
@@ -71,3 +71,5 @@ moneyTransfer({ amount: 100, kind: 'domestic' });
 
 console.log('--- International Workflow ---');
 moneyTransfer({ amount: 100, kind: 'international' });
+
+module.exports = { pipe, branch };
\ No newline at end of file
diff --git a/JavaScript/4-functional.test.js b/JavaScript/4-functional.test.js
new file mode 100644
index 0000000..c61b745
--- /dev/null
+++ b/JavaScript/4-functional.test.js
@@ -0,0 +1,176 @@
+const { pipe, branch } = require('./4-functional');
+
+describe('pipe function', () => {
+  test('should apply functions in sequence', () => {
+    const add1 = (x) => x + 1;
+    const multiply2 = (x) => x * 2;
+    const subtract3 = (x) => x - 3;
+    
+    const pipeline = pipe(add1, multiply2, subtract3);
+    const result = pipeline(5);
+    
+    // 5 -> 6 -> 12 -> 9
+    expect(result).toBe(9);
+  });
+
+  test('should work with single function', () => {
+    const double = (x) => x * 2;
+    const pipeline = pipe(double);
+    
+    expect(pipeline(5)).toBe(10);
+  });
+
+  test('should work with no functions (identity)', () => {
+    const pipeline = pipe();
+    
+    expect(pipeline(42)).toBe(42);
+    expect(pipeline('test')).toBe('test');
+  });
+
+  test('should work with object transformations', () => {
+    const addField = (obj) => ({ ...obj, added: true });
+    const incrementId = (obj) => ({ ...obj, id: obj.id + 1 });
+    
+    const pipeline = pipe(addField, incrementId);
+    const result = pipeline({ id: 1, name: 'test' });
+    
+    expect(result).toEqual({ id: 2, name: 'test', added: true });
+  });
+
+  test('should handle async functions', async () => {
+    const asyncAdd = async (x) => x + 1;
+    const asyncMultiply = async (x) => x * 2;
+    
+    const pipeline = pipe(asyncAdd, asyncMultiply);
+    const result = await pipeline(5);
+    
+    expect(result).toBe(12);
+  });
+
+  test('should preserve function execution order', () => {
+    const log = [];
+    const fn1 = (x) => { log.push('fn1'); return x; };
+    const fn2 = (x) => { log.push('fn2'); return x; };
+    const fn3 = (x) => { log.push('fn3'); return x; };
+    
+    const pipeline = pipe(fn1, fn2, fn3);
+    pipeline('test');
+    
+    expect(log).toEqual(['fn1', 'fn2', 'fn3']);
+  });
+});
+
+
+describe('branch function', () => {
+  test('should execute correct branch based on request property', () => {
+    const mockDomestic = jest.fn((req) => ({ ...req, processed: 'domestic' }));
+    const mockInternational = jest.fn((req) => ({ ...req, processed: 'international' }));
+    
+    const brancher = branch({
+      type: {
+        domestic: mockDomestic,
+        international: mockInternational
+      }
+    });
+    
+    const request = { type: 'domestic', amount: 100 };
+    const result = brancher(request);
+    
+    expect(mockDomestic).toHaveBeenCalledWith(request);
+    expect(mockInternational).not.toHaveBeenCalled();
+    expect(result.processed).toBe('domestic');
+  });
+
+  test('should work with different branch keys', () => {
+    const mockHandlerA = jest.fn((req) => ({ ...req, result: 'A' }));
+    const mockHandlerB = jest.fn((req) => ({ ...req, result: 'B' }));
+    
+    const brancher = branch({
+      category: {
+        typeA: mockHandlerA,
+        typeB: mockHandlerB
+      }
+    });
+    
+    const request = { category: 'typeB', data: 'test' };
+    const result = brancher(request);
+    
+    expect(mockHandlerB).toHaveBeenCalledWith(request);
+    expect(mockHandlerA).not.toHaveBeenCalled();
+    expect(result.result).toBe('B');
+  });
+
+  test('should throw error when no matching way found', () => {
+    const brancher = branch({
+      type: {
+        domestic: (req) => req,
+        international: (req) => req
+      }
+    });
+    
+    const request = { type: 'unknown', amount: 100 };
+    
+    expect(() => brancher(request)).toThrow('No matching way found');
+  });
+
+  test('should throw error when property is missing', () => {
+    const brancher = branch({
+      type: {
+        domestic: (req) => req,
+        international: (req) => req
+      }
+    });
+    
+    const request = { amount: 100 }; // missing 'type' property
+    
+    expect(() => brancher(request)).toThrow('No matching way found');
+  });
+
+  test('should work with complex branch handlers', () => {
+    const complexHandler = pipe(
+      (req) => ({ ...req, step1: true }),
+      (req) => ({ ...req, step2: true })
+    );
+    
+    const brancher = branch({
+      workflow: {
+        complex: complexHandler,
+        simple: (req) => ({ ...req, simple: true })
+      }
+    });
+    
+    const request = { workflow: 'complex', id: 1 };
+    const result = brancher(request);
+    
+    expect(result).toEqual({
+      workflow: 'complex',
+      id: 1,
+      step1: true,
+      step2: true
+    });
+  });
+
+  test('should handle numeric keys', () => {
+    const brancher = branch({
+      status: {
+        1: (req) => ({ ...req, result: 'active' }),
+        0: (req) => ({ ...req, result: 'inactive' })
+      }
+    });
+    
+    const result = brancher({ status: 1 });
+    expect(result.result).toBe('active');
+  });
+
+  test('should handle boolean keys', () => {
+    const brancher = branch({
+      isActive: {
+        true: (req) => ({ ...req, result: 'enabled' }),
+        false: (req) => ({ ...req, result: 'disabled' })
+      }
+    });
+    
+    const result = brancher({ isActive: true });
+    expect(result.result).toBe('enabled');
+  });
+});
\ No newline at end of file