Fix calculator empty input handling and add tests

gradio_calculator.py

@@ -20,7 +20,7 @@ def calculate(num1, num2, operation):
             return "Invalid operation"
 
         return result
-    except ValueError:
+    except (ValueError, TypeError):
         return "Please enter valid numbers"
 
 

test_calculator.py

@@ -0,0 +1,49 @@
+import sys
+import unittest
+from unittest.mock import MagicMock
+
+# Ensure test can run even if gradio is not installed in the environment
+if "gradio" not in sys.modules:
+    sys.modules["gradio"] = MagicMock()
+
+from gradio_calculator import calculate
+
+
+class TestCalculator(unittest.TestCase):
+
+    def test_arithmetic_operations(self):
+        self.assertEqual(calculate(10, 5, "+"), 15.0)
+        self.assertEqual(calculate(10, 5, "-"), 5.0)
+        self.assertEqual(calculate(10, 5, "*"), 50.0)
+        self.assertEqual(calculate(10, 5, "/"), 2.0)
+
+    def test_division_by_zero(self):
+        self.assertEqual(calculate(10, 0, "/"), "Cannot divide by zero")
+        self.assertEqual(calculate(10, 0.0, "/"), "Cannot divide by zero")
+        self.assertEqual(calculate(10, -0.0, "/"), "Cannot divide by zero")
+
+    def test_invalid_string_inputs(self):
+        self.assertEqual(calculate("abc", 5, "+"), "Please enter valid numbers")
+        self.assertEqual(calculate(10, "xyz", "+"), "Please enter valid numbers")
+        self.assertEqual(calculate("abc", "xyz", "+"), "Please enter valid numbers")
+
+    def test_empty_first_input(self):
+        # Case 1 from confirmed bug: calculate(None, 5, "+")
+        self.assertEqual(calculate(None, 5, "+"), "Please enter valid numbers")
+
+    def test_empty_second_input(self):
+        # Case 2 from confirmed bug: calculate(10, None, "+")
+        self.assertEqual(calculate(10, None, "+"), "Please enter valid numbers")
+
+    def test_both_inputs_empty(self):
+        # Case 3 from confirmed bug: calculate(None, None, "+")
+        self.assertEqual(calculate(None, None, "+"), "Please enter valid numbers")
+
+    def test_invalid_operation(self):
+        self.assertEqual(calculate(10, 5, "%"), "Invalid operation")
+        self.assertEqual(calculate(10, 5, None), "Invalid operation")
+
+
+if __name__ == "__main__":
+    unittest.main()
+