What exactly is unit testing? How should they be done?

Unit testing is generally done by either developers or testers. There is no absolute standard for who should do it, it depends on the company.

Unit tests are implemented in the following ways: manual static checking, dynamic execution tracking.

Manual static checking: it is usually called "code walking", mainly to ensure the correctness of the code logic.

Dynamic execution tracking: that is, to run the program code to check whether the actual results and expected results are consistent.

Developers do unit testing:

Advantages: developers are the most familiar with the code, and developers have relatively strong programming skills, so developers write their own unit tests are more efficient and coverage.

Disadvantages: developers usually write business code to spend a lot of time, sometimes there is really no time to write unit tests; and most developers do not have too good testing ideas, unit testing may be just write the simplest use case on the end; write their own code to test, often are not reliable.

Testers do unit testing:

Advantages: testers have a more systematic testing ideas, can better ensure the coverage of use cases. And by writing single test tests can better understand the specific code structure, flow, for the subsequent business testing is also very favorable.

Disadvantages: testers programming skills are relatively weak, if different programming is unable to carry out unit testing. And testers are not as familiar with the code as developers, and the efficiency will be lower.