What is unit testing?

Unit testing is a way used to ensure that individual units or components of software code perform as expected. It isolates a section of a code and verify its correctness.A unit may be an individual function, method, procedure, module or object. Unit testing is the first level of testing in SDLC, STLC, V model and also it is usually performed by developers. Unit testing helps to identify bugs in early stages of software development life cycle and it helps to save money,time.