rename test_index.py to test_index_document.py

.cursor/skills/tdd/tests.md

@@ -0,0 +1,60 @@
+# Good and Bad Tests
+
+## Good Tests
+
+**Integration-style**: Test through real interfaces, not mocks of internal parts.
+
+```python
+# GOOD: Tests observable behavior
+def test_user_can_checkout_with_valid_cart():
+    cart = create_cart()
+    cart.add(product)
+    result = checkout(cart, payment_method)
+    assert result.status == "confirmed"
+
+```
+
+Characteristics:
+
+* Tests behavior users/callers care about
+* Uses public API only
+* Survives internal refactors
+* Describes WHAT, not HOW
+* One logical assertion per test
+
+## Bad Tests
+
+**Implementation-detail tests**: Coupled to internal structure.
+
+```python
+# BAD: Tests implementation details
+def test_checkout_calls_payment_service_process():
+    mock_payment = MagicMock()
+    checkout(cart, mock_payment)
+    mock_payment.process.assert_called_with(cart.total)
+
+```
+
+Red flags:
+
+* Mocking internal collaborators
+* Testing private methods
+* Asserting on call counts/order
+* Test breaks when refactoring without behavior change
+* Test name describes HOW not WHAT
+* Verifying through external means instead of interface
+
+```python
+# BAD: Bypasses interface to verify
+def test_create_user_saves_to_database():
+    create_user({"name": "Alice"})
+    row = db.query("SELECT * FROM users WHERE name = ?", ["Alice"])
+    assert row is not None
+
+# GOOD: Verifies through interface
+def test_create_user_makes_user_retrievable():
+    user = create_user({"name": "Alice"})
+    retrieved = get_user(user.id)
+    assert retrieved.name == "Alice"
+
+```