如何验证django自定义模型字段属性？

from django.test import TestCase
from django.db import models
from django.core.exceptions import ValidationError

class CustomField(models.Field):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def validate(self, value, model_instance):
        # 在这里编写验证逻辑
        if value < 0:
            raise ValidationError("值不能为负数")

    def deconstruct(self):
        name, path, args, kwargs = super().deconstruct()
        return name, path, args, kwargs

class CustomFieldTest(TestCase):
    def test_custom_field_validation(self):
        field = CustomField()
        model_instance = None
        valid_value = 10
        invalid_value = -5

        # 验证有效值
        try:
            field.validate(valid_value, model_instance)
        except ValidationError:
            self.fail("验证失败")

        # 验证无效值
        with self.assertRaises(ValidationError):
            field.validate(invalid_value, model_instance)

python manage.py test