Improve code coverage to 70%

[forfreeday]

Rationale

Why should this feature exist?

To improve the test case coverage of your code, cover as much as possible.

Implementation

database

• test(db): add test for db #5461
• test(db): add test for db #5463

api

• test(rpc): add test cases for RPC interfaces #5471
• test(api): add test cases of Wallet #5442

net

• test(net): add message handler test cases #5459

Are you willing to implement this feature?
Yes, I would like to complete these use cases and would like to have more people participate in them.

[xxo1shine]

@forfreeday This is a good idea, it is really necessary to increase the unit test rate to avoid introducing bugs.

[forfreeday]

@wubin01

Yes, this will be ongoing, with 70% coverage in the first phase

[forfreeday]

Current coverage: 66.48%.
Continuously adding test cases, expected to reach 70% coverage in June.