添加课程相关的测试模块
Merge branch 'develop' into feature/test_create_lesson
Merge branch 'develop' into feature/test_create_lesson
修改了一个数据库的默认值，使得单元测试正常
修改了代码风格和命名规范
修改了代码风格
Merge branch 'feature/test_create_lesson' into develop

Conflicts:
	experiment/tests.py