Unit testing is the type of testing where individual units are tested rather whole product. This can be also considered as the finest possible approach for the testing where minute elements are being checked. This part of testing is done during the coding or development part of the process. Through this way a part of code is been checked before it gets functionally active in the application. In most of the cases, unit testing is performed using by the developer.
In all models of software testing, this is the first level of testing prior to integration testing so its value is quite important. This is actually a white box testing technique that is performed mainly by the developer. Nowadays, in some large scale projects, developer and testers work together to get the things ready for unit testing.
How code is written for the product is quite important? Its hierarchy and arrangement of elements for the entire program is quite important for programming and its result. If you have a good developer working for your project then there will be very less or no error for your project. This is always a good approach to have errors sorted prior to going to final testing phase.