diff --git a/pyproject.toml b/pyproject.toml
index 31551a3e1..1d5b859eb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -18,3 +18,6 @@ bindings = "pyo3"
 python-source = "python"
 module-name = "cocoindex._engine"
 features = ["pyo3/extension-module"]
+
+[project.optional-dependencies]
+test = ["pytest"]
\ No newline at end of file
diff --git a/python/cocoindex/tests/__init__.py b/python/cocoindex/tests/__init__.py
new file mode 100644
index 000000000..8b1378917
--- /dev/null
+++ b/python/cocoindex/tests/__init__.py
@@ -0,0 +1 @@
+
diff --git a/python/cocoindex/tests/test_convert.py b/python/cocoindex/tests/test_convert.py
new file mode 100644
index 000000000..51cda929a
--- /dev/null
+++ b/python/cocoindex/tests/test_convert.py
@@ -0,0 +1,69 @@
+import dataclasses
+import uuid
+import datetime
+from dataclasses import dataclass
+import pytest
+from cocoindex.convert import to_engine_value
+
+@dataclass
+class Order:
+    order_id: str
+    name: str
+    price: float
+
+@dataclass
+class Basket:
+    items: list
+
+@dataclass
+class Customer:
+    name: str
+    order: Order
+
+def test_to_engine_value_basic_types():
+    assert to_engine_value(123) == 123
+    assert to_engine_value(3.14) == 3.14
+    assert to_engine_value("hello") == "hello"
+    assert to_engine_value(True) is True
+
+def test_to_engine_value_uuid():
+    u = uuid.uuid4()
+    assert to_engine_value(u) == u.bytes
+
+def test_to_engine_value_date_time_types():
+    d = datetime.date(2024, 1, 1)
+    assert to_engine_value(d) == d
+    t = datetime.time(12, 30)
+    assert to_engine_value(t) == t
+    dt = datetime.datetime(2024, 1, 1, 12, 30)
+    assert to_engine_value(dt) == dt
+
+def test_to_engine_value_struct():
+    order = Order(order_id="O123", name="mixed nuts", price=25.0)
+    assert to_engine_value(order) == ["O123", "mixed nuts", 25.0]
+
+def test_to_engine_value_list_of_structs():
+    orders = [Order("O1", "item1", 10.0), Order("O2", "item2", 20.0)]
+    assert to_engine_value(orders) == [["O1", "item1", 10.0], ["O2", "item2", 20.0]]
+
+def test_to_engine_value_struct_with_list():
+    basket = Basket(items=["apple", "banana"])
+    assert to_engine_value(basket) == [["apple", "banana"]]
+
+def test_to_engine_value_nested_struct():
+    customer = Customer(name="Alice", order=Order("O1", "item1", 10.0))
+    assert to_engine_value(customer) == ["Alice", ["O1", "item1", 10.0]]
+
+def test_to_engine_value_empty_list():
+    assert to_engine_value([]) == []
+    assert to_engine_value([[]]) == [[]]
+
+def test_to_engine_value_tuple():
+    assert to_engine_value(()) == []
+    assert to_engine_value((1, 2, 3)) == [1, 2, 3]
+    assert to_engine_value(((1, 2), (3, 4))) == [[1, 2], [3, 4]]
+    assert to_engine_value(([],)) == [[]]
+    assert to_engine_value(((),)) == [[]]
+
+def test_to_engine_value_none():
+    assert to_engine_value(None) is None