diff --git a/add.go b/add.go
new file mode 100644
index 0000000..4c2e091
--- /dev/null
+++ b/add.go
@@ -0,0 +1,9 @@
+package main
+
+func addNumbers(a int, b int) int {
+    return a + b
+}
+
+func addComplexNumbers(a complex128, b complex128) complex128 {
+    return a + b
+}
diff --git a/add_test.go b/add_test.go
new file mode 100644
index 0000000..891fef3
--- /dev/null
+++ b/add_test.go
@@ -0,0 +1,26 @@
+package main
+
+import "testing"
+
+func TestAddComplexNumbers(t *testing.T) {
+    testCases := []struct {
+        name     string
+        a, b     complex128
+        expected complex128
+    }{
+        {"add zero", 0, 0, 0},
+        {"add positive numbers", 1 + 2i, 3 + 4i, 4 + 6i},
+        {"add negative numbers", -1 - 2i, -3 - 4i, -4 - 6i},
+        {"add mixed numbers", -1 + 2i, 3 - 4i, 2 - 2i},
+        {"add large numbers", 1 + 123456789i, 2 + 987654321i, 3 + 1111111110i},
+    }
+
+    for _, tc := range testCases {
+        t.Run(tc.name, func(t *testing.T) {
+            result := addComplexNumbers(tc.a, tc.b)
+            if result != tc.expected {
+                t.Errorf("addComplexNumbers(%v, %v) = %v; want %v", tc.a, tc.b, result, tc.expected)
+            }
+        })
+    }
+}