tl;dr No, testers don't write Unit Tests for code developed by developers, but some developers/testers write automated tests that are not Unit Tests. It depends on the definition of "Unit Test". There is still a large number of people who call things that really aren't Unit Tests "Unit Tests".

Can tester write unit test?

Unit testing is a type of white-box testing. Integration testing is a type of black-box testing. It is performed by software developers or even by testers. It is performed by testers.

Who should write the unit tests?

Closed 6 years ago. Should unit tests be written by the developer who wrote the code or someone else ? And how effective is writing units tests as a method of learning a new system ? The unit tests should be written by the developer who writes the code, before she writes the code.