test(group): Add unit tests for DummyGroup class

Creates test_group.py with comprehensive unit tests for DummyGroup,
covering initialization, basic operations, and pairing functionality.

src/group.py

@@ -3,7 +3,7 @@ class DummyGroup:
     def __init__(self, field):
         self.field = field
 
-    def identity():
+    def identity(self):
         return self.field.zero()
 
     def generator(self):

tests/test_group.py

@@ -0,0 +1,49 @@
+import unittest
+from unittest.mock import Mock
+import sys
+
+sys.path.append('../src')
+sys.path.append('src')
+
+from group import DummyGroup
+
+class TestDummyGroup(unittest.TestCase):
+    def setUp(self):
+        self.mock_field = Mock()
+        self.mock_field.zero.return_value = 0
+        self.mock_field.primitive_element.return_value = 1
+        self.mock_field.order.return_value = 100
+        self.group = DummyGroup(self.mock_field)
+
+    def test_init(self):
+        self.assertEqual(self.group.field, self.mock_field)
+
+    def test_identity(self):
+        self.assertEqual(self.group.identity(), 0)
+
+    def test_generator(self):
+        self.assertEqual(self.group.generator(), 1)
+
+    def test_exp(self):
+        self.assertEqual(self.group.exp(2, 3), 6)
+
+    def test_scalar_mul_single(self):
+        self.assertEqual(self.group.scalar_mul(2, 3), 6)
+
+    def test_scalar_mul_list(self):
+        self.assertEqual(self.group.scalar_mul([1, 2, 3], 2), [2, 4, 6])
+
+    def test_add(self):
+        self.assertEqual(self.group.add(2, 3), 5)
+
+    def test_sub(self):
+        self.assertEqual(self.group.sub(5, 3), 2)
+
+    def test_order(self):
+        self.assertEqual(self.group.order(), 100)
+
+    def test_pairing(self):
+        self.assertEqual(DummyGroup.pairing(2, 3), 6)
+
+if __name__ == '__main__':
+    unittest.main()