1. Requirements:
Verify the correctness of a city phone number.
2. Requirements:
1) Area code: empty or three digits.
2) Prefix code: a number that is not "0" and does not start with "1".
3) Suffix code: four digits.
Experience: In any use case, the requirements are nothing more than length, type, and rules.
3. Writing test cases:
Firstly analyze the requirements, secondly determine the effective equivalence and invalid equivalence, and finally design the test data writing use cases.
Test case:
