Django序列化器测试：含用户信息的文件上传请求报错解决

我尝试测试包含用户信息的文件上传接口，编写了如下测试代码：

@deconstructible
class FileGenerator:

    @staticmethod
    def generate_text_file(file_ending='txt'):
        file_content = b'some test string'
        file = io.BytesIO(file_content)
        file.name = f'test.{file_ending}'
        file.seek(0)
        return file

def test_this(self, api_client, login_as):
    user = login_as('quality-controller')
    url = reverse('test-list')
    organization = Organization(name="test")
    organization.save()

    data = {
        "organization": organization.id,
        "import_file": FileGenerator.generate_text_file('txt'),
        "user": {
            "id": user.id,
            "username": user.username,
        }
    }

    response = api_client.post(url, data, format='json')

使用format='json'发送请求时，收到错误：

b'{"import_file": ["The submitted data was not a file. Check the encoding type on the form."]}'

改用format='multipart'时，又收到错误：

AssertionError: Test data contained a dictionary value for key 'user', but multipart uploads do not support nested data. You may want to consider using format='json' in this test case.

方法1：扁平化嵌套的user数据（适配multipart格式） #

multipart/form-data不支持嵌套字典，直接把user的字段拆成顶层键值对，保持文件字段不变即可：

data = {
    "organization": organization.id,
    "import_file": FileGenerator.generate_text_file('txt'),
    "user_id": user.id,
    "user_username": user.username,
}

response = api_client.post(url, data, format='multipart')

后端接口需要同步调整，要么直接接收这些扁平化字段，要么在逻辑层将字段重新组装成user字典。

方法2：Base64编码文件内容（适配JSON格式） #

如果后端支持，把文件内容转成Base64字符串嵌入JSON数据中发送：

import base64

def test_this(self, api_client, login_as):
    user = login_as('quality-controller')
    url = reverse('test-list')
    organization = Organization(name="test")
    organization.save()

    # 将文件内容编码为Base64字符串
    file_content = b'some test string'
    base64_file = base64.b64encode(file_content).decode('utf-8')

    data = {
        "organization": organization.id,
        "import_file": {
            "filename": "test.txt",
            "content": base64_file,
            "content_type": "text/plain"
        },
        "user": {
            "id": user.id,
            "username": user.username,
        }
    }

    response = api_client.post(url, data, format='json')

后端需要对应做解码处理，把Base64字符串还原为文件内容。

方法3：将嵌套字段序列化为JSON字符串（适配multipart格式） #

把user字典转成JSON字符串作为顶层字段值，后端再反序列化解析：

import json

data = {
    "organization": organization.id,
    "import_file": FileGenerator.generate_text_file('txt'),
    "user": json.dumps({
        "id": user.id,
        "username": user.username,
    }),
}

response = api_client.post(url, data, format='multipart')

后端接口中用json.loads()解析user字段的值，即可得到原字典结构。

内容的提问来源于stack exchange，提问作者Andreas