Differentiate between White Box and Black Box Testing. 

Ans:
White box testing strategy deals with the internal logic and structure of the code.
White box testing also known as glass, structural, open box or clear box testing,
tests code written, branches, paths, statements and internal logic of the code etc.
In order to implement white box testing, the tester has to deal with the code and
hence is needed to possess knowledge of coding and logic i.e. internal working of
the code. White box test also needs the tester to look into the code and find out
which unit/statement/chunk of the code is malfunctioning. White box testing is
applicable at unit, integration and system level however it is mainly done at unit
level.
Black box testing Black-box test design treats the system as a "black-box", so it
doesn't explicitly use knowledge of the internal structure. It takes an external
perspective of the test object to derive test cases. These tests can be functional or
non-functional, though usually functional. The test designer selects valid and
invalid input and determines the correct output. There is no knowledge of the test
object's internal structure.
This method of test design is applicable to all levels of software testing: unit,
integration, functional testing, system and acceptance.