Software testing involves finding bugs and errors in applications. There are two main types of testing methodologies: black box testing and white box testing. Black box testing focuses on inputs and outputs without considering internal code, while white box testing examines internal code structures. Common black box techniques include state transition diagrams, decision tables, use case testing, equivalence partitioning, and boundary value analysis. White box techniques include basic path testing and loop testing to achieve high code coverage. Both approaches have advantages and disadvantages related to code visibility, tester expertise, and testing efficiency.