By design we mean to create a plan for how to implement an idea and technique is a method or way for performing a task. So, Test Design is creating a set of inputs for given software that will provide a set of expected outputs. The idea is to ensure that the system is working good enough and it can be released with as few problems as possible for the average user.
Broadly speaking there are two main categories of Test Design Techniques. They are:
Below is the tree structure of the testing techniques: