feat: add comprehensive custom API tests

- Add TestCustomAPI class with multiple test scenarios
- Include parametrized tests for different item IDs
- Add fixture examples for reusable test data
- Test both valid and invalid input validation
- Cover GET, POST endpoints with success/error cases

tests/test_custom_api.py

@@ -0,0 +1,154 @@
+"""
+自定义API测试
+这是一个示例测试文件，展示如何在FastAPI项目中编写测试
+"""
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+from pydantic import BaseModel
+from typing import Optional
+
+
+# 创建一个简单的FastAPI应用用于测试
+app = FastAPI()
+
+
+# 定义数据模型
+class Item(BaseModel):
+    name: str
+    price: float
+    is_offer: bool = False
+
+
+class User(BaseModel):
+    username: str
+    email: str
+
+
+# 定义API路由
+@app.get("/")
+def read_root():
+    return {"message": "Hello Custom API"}
+
+
+@app.get("/items/{item_id}")
+def read_item(item_id: int, q: Optional[str] = None):
+    return {"item_id": item_id, "q": q}
+
+
+@app.post("/items/")
+def create_item(item: Item):
+    return {"item": item, "status": "created"}
+
+
+@app.get("/users/{user_id}")
+def get_user(user_id: int):
+    return {"user_id": user_id, "username": f"user_{user_id}"}
+
+
+# 创建测试客户端
+client = TestClient(app)
+
+
+# 测试用例
+class TestCustomAPI:
+    """自定义API测试类"""
+    
+    def test_read_root(self):
+        """测试根路径"""
+        response = client.get("/")
+        assert response.status_code == 200
+        assert response.json() == {"message": "Hello Custom API"}
+    
+    def test_read_item_with_params(self):
+        """测试带参数的商品查询"""
+        response = client.get("/items/5?q=somequery")
+        assert response.status_code == 200
+        assert response.json() == {"item_id": 5, "q": "somequery"}
+    
+    def test_read_item_without_params(self):
+        """测试不带查询参数的商品查询"""
+        response = client.get("/items/10")
+        assert response.status_code == 200
+        assert response.json() == {"item_id": 10, "q": None}
+    
+    def test_create_item(self):
+        """测试创建商品"""
+        item_data = {
+            "name": "Test Item",
+            "price": 99.99,
+            "is_offer": True
+        }
+        response = client.post("/items/", json=item_data)
+        assert response.status_code == 200
+        response_data = response.json()
+        assert response_data["status"] == "created"
+        assert response_data["item"]["name"] == "Test Item"
+        assert response_data["item"]["price"] == 99.99
+        assert response_data["item"]["is_offer"] is True
+    
+    def test_get_user(self):
+        """测试获取用户信息"""
+        response = client.get("/users/123")
+        assert response.status_code == 200
+        assert response.json() == {"user_id": 123, "username": "user_123"}
+    
+    @pytest.mark.parametrize("item_id,expected_id", [
+        (1, 1),
+        (42, 42),
+        (999, 999),
+    ])
+    def test_read_item_parametrized(self, item_id, expected_id):
+        """参数化测试：测试不同的商品ID"""
+        response = client.get(f"/items/{item_id}")
+        assert response.status_code == 200
+        assert response.json()["item_id"] == expected_id
+    
+    def test_invalid_item_id(self):
+        """测试无效的商品ID"""
+        response = client.get("/items/not_a_number")
+        assert response.status_code == 422  # 验证错误
+    
+    def test_create_item_invalid_data(self):
+        """测试创建商品时的无效数据"""
+        invalid_data = {
+            "name": "Test Item",
+            # 缺少必需的price字段
+            "is_offer": True
+        }
+        response = client.post("/items/", json=invalid_data)
+        assert response.status_code == 422  # 验证错误
+
+
+# 独立的测试函数（不在类中）
+def test_app_startup():
+    """测试应用启动"""
+    assert app.title == "FastAPI"
+
+
+def test_openapi_schema():
+    """测试OpenAPI schema生成"""
+    response = client.get("/openapi.json")
+    assert response.status_code == 200
+    schema = response.json()
+    assert "openapi" in schema
+    assert "info" in schema
+
+
+# Fixture示例
+@pytest.fixture
+def sample_item():
+    """测试用的示例商品数据"""
+    return {
+        "name": "Sample Item",
+        "price": 50.0,
+        "is_offer": False
+    }
+
+
+def test_with_fixture(sample_item):
+    """使用fixture的测试"""
+    response = client.post("/items/", json=sample_item)
+    assert response.status_code == 200
+    response_data = response.json()
+    assert response_data["item"]["name"] == sample_item["name"]