diff --git a/drone_test/__init__.py b/drone_test/__init__.py
new file mode 100644
index 0000000..936bd02
--- /dev/null
+++ b/drone_test/__init__.py
@@ -0,0 +1,12 @@
+"""Python module to test drone builds"""
+
+import math
+
+def circle_area(radius: float):
+    """Calculate the area of a circle
+
+    :param radius: circle radius
+    :raises ValueError: radius is negative
+    :return: area of the circle
+    """
+    return math.pi * radius ** 2
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_circle_area.py b/tests/test_circle_area.py
new file mode 100644
index 0000000..d0f8d56
--- /dev/null
+++ b/tests/test_circle_area.py
@@ -0,0 +1,15 @@
+from unittest import TestCase
+import math
+
+from drone_test import circle_area
+
+class CircleAreaTest(TestCase):
+    def test_area_1(self):
+        self.assertEqual(circle_area(1), math.pi)
+
+    def test_area_2(self):
+        self.assertEqual(circle_area(2), math.pi * 4)
+
+    def test_negative(self):
+        with self.assertRaises(ValueError):
+            circle_area(-1)