As you can see on the Internet, the granularity criteria for writing test cases

I. interface specifications
1. Whether the font, size, color, and arrangement of the entire software field are consistent
2. Whether the entire software field is followed by a colon (if so, whether it belongs to the same font)

Ii. granularity criteria for case writing
1. for operations that do not act as a complete business flow, such as adding, deleting, or modifying, each operation (such as adding) serves as a use case.
2. for complete operations on business functions, the purpose of implementing a business function is used as a case.
3. For closely related business functions, the associated business functions are implemented as a use case.
4. Operations in exceptional circumstances are used as a case.
5. Data Processing for operations in exceptional circumstances is used as a case.