Software Testing : Black box and White box Techniques

Black-box and white-box are test design methods. Black-box test design treats the system as a "black-box", so it doesn’t explicitly use knowledge of the internal structure. Black-box test design is usually described as focusing on testing functional requirements. White-box test design allows one to peek inside the "box", and it focuses specifically on using internal knowledge of the software to guide the selection of test data.

While black-box and white-box are terms that are still in popular use, many people prefer the terms "behavioral" and "structural". Behavioral test design is slightly different from black-box test design because the use of internal knowledge isn't strictly forbidden, but it's still discouraged. In practice, it hasn't proven useful to use a single test design method. One has to use a mixture of different methods so that they aren't hindered by the limitations of a particular one. Some call this "gray-box" or "translucent-box" test design, but others wish we'd stop talking about boxes altogether.

It is important to understand that these methods are used during the test design phase, and their influence is hard to see in the tests once they're implemented. Note that any level of testing (unit testing, system testing, etc.) can use any test design methods. Unit testing is usually associated with structural test design, but this is because testers usually don't have well-defined requirements at the unit level to validate.

What is Black box Software Testing?

It is a software testing technique whereby the internal workings of the item being tested are not known by the tester. For example, in a black box test on software design the tester only knows the inputs and what the expected outcomes should be and not how the program arrives at those outputs. The tester does not ever examine the programming code and does not need any further knowledge of the program other than its specifications.

The advantages of this type of testing include:

· The test is unbiased because the designer and the tester are independent of each other.

· The tester does not need knowledge of any specific programming languages.

· The test is done from the point of view of the user, not the designer.

· Test cases can be designed as soon as the specifications are complete.

The disadvantages of this type of testing include:

· The test can be redundant if the software designer has already run a test case.

· The test cases are difficult to design.

· Testing every possible input stream is unrealistic because it would take an inordinate amount of time; therefore, many program paths will go untested.

Black box Software Testing Full Lecture Notes

What is a White box Software Testing?

This is a software testing technique whereby explicit knowledge of the internal workings of the item being tested is used to select the test data. Unlike black box testing, white box testing uses specific knowledge of programming code to examine outputs. The test is accurate only if the tester knows what the program is supposed to do. He or she can then see if the program diverges from its intended goal. White box testing does not account for errors caused by omission, and all visible code must also be readable.

Software Testing Techniques 

(Includes both Black and White box techniques)