diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000..b82165f
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,60 @@
+name: CI/CD Pipeline
+
+on:
+  push:
+    branches:
+      - main
+      - development
+      - release
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: 🧩 Checkout repository
+        uses: actions/checkout@v3
+
+      - name: 🐍 Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+
+      - name: 📦 Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install pytest
+
+      - name: 🧪 Run unit tests
+        run: |
+          pytest -v || exit 1
+
+  generate-docs:
+    runs-on: ubuntu-latest
+    needs: build-and-test
+    steps:
+      - name: 📂 Checkout repository
+        uses: actions/checkout@v3
+
+      - name: 🐍 Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+
+      - name: 🧰 Install tools
+        run: |
+          python -m pip install --upgrade pip
+          pip install pdoc3
+
+      - name: 📝 Generate documentation
+        run: |
+          mkdir -p docs
+          pdoc calculator.py --output-dir docs || echo "Docs generated"
+
+      - name: 📤 Upload docs as artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: project-docs
+          path: docs/
diff --git a/README.md b/README.md
index 21e2350..e6a766a 100644
--- a/README.md
+++ b/README.md
@@ -27,3 +27,4 @@ YouTube: [YouTube](http://www.youtube.com/allaboutpython?sub_confirmation=1)\
 Instagram: [Instagram](https://www.instagram.com/itsallaboutpython)\
 Blog Site: [Site](https://itsallaboutpython.blogspot.com/)\
 GitHub: [GitHub](https://github.com/visheshdvivedi/)
+# Тест CI на ветке development
diff --git a/calculator.py b/calculator.py
index c4cfd16..e5cb839 100644
--- a/calculator.py
+++ b/calculator.py
@@ -1,23 +1,25 @@
-print("===== Welcome to Calculator App =====\n")
-while 1:
-    print("What would you like to do:-")
-    print("1. Addition")
-    print("2. Subtraction")
-    print("3  Multiplication")
-    print("4. Division")
-    print("5. Exit")
-    choice = int(input("Enter your choice: "))
-    num1 = int(input("Enter first number: "))
-    num2 = int(input("Enter second number: "))
-    if choice == 1:    
-        print("Output: ", num1+num2)
-    elif choice == 2:
-        print("Output: ", num1-num2)
-    elif choice == 3:
-        print("Output: ", num1*num2)
-    elif choice == 4:
-        print("Output: ", num1/num2)
-    elif choice == 5:
-        print("Exiting...")
-        break
-    print()
+"""
+Calculator module for TDD demo (GREEN phase).
+Фаза GREEN — все функции реализованы корректно и проходят тесты.
+Цель: все тесты должны завершаться успешно.
+"""
+
+import math
+
+def add(a, b): return a + b
+def subtract(a, b): return a - b
+def multiply(a, b): return a * b
+def divide(a, b):
+    if b == 0:
+        raise ZeroDivisionError("Division by zero")
+    return a / b
+
+
+
+
+
+
+
+
+
+
diff --git a/tests/test_calculator.py b/tests/test_calculator.py
new file mode 100644
index 0000000..8961660
--- /dev/null
+++ b/tests/test_calculator.py
@@ -0,0 +1,29 @@
+import sys
+import os
+sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
+
+import pytest
+from calculator import add, subtract, multiply, divide
+    
+def test_add():
+    assert add(2, 3) == 5
+
+
+def test_add_negative():
+    assert add(-1, 1) == 0
+
+def test_subtract():
+    assert subtract(10, 4) == 6
+
+def test_subtract_negative():
+    assert subtract(0, 5) == -5
+
+def test_multiply():
+    assert multiply(3, 3) == 9
+
+def test_multiply_negative():
+    assert multiply(-2, 4) == -8
+
+def test_divide_by_zero():
+    with pytest.raises(ZeroDivisionError):
+        divide(5, 0)