What is a software Testing Methodology?

A methodology is a package of methods. In simple words, it’s a bundle of practical ideas and proven practises which help in efficient software project management.

Testing is the integral part of software development. Poor testing methodologies lead to unstable products and unpredictable development times. It is more important than ever to have a robust testing methodology for making sure that software products/systems being developed have been fully tested to make sure they meet their specified requirements and can successfully operate in all the anticipated environments with the required usability and security.

Standard development methodologies describe a set of general testing mechanisms which must be incorporated in the product development lifecycle. These mechanisms start from testing very small of code piece by piece to testing the whole application functionality in the end.

There are different methods which can be used for software testing

  1. Black Box Testing
  2. White Box testing
  3. Grey Box Testing

 

Black Box Testing: Black box testing is also known as behavioral Testing, is a software testing method in which the internal structure/ design/ implementation of the item being tested is not known to the tester. These tests can be functional or non-functional, though usually functional.

Software_Testing_methodology_1

 

Black box testing treats the system as a “black-box”, so it doesn’t explicitly use Knowledge of the internal structure or code. Or in other words the Test engineer need not know the internal working of the “Black box” or application. Main focus in black box testing is on functionality of the system as a whole. For example: an operating system like Windows, a website like Google ,a database like Oracle or even your own custom application. Under Black Box Testing, you can test these applications by just focusing on the inputs and outputs without knowing their internal code implementation.

This method attempts to find errors in the following categories:

  • Incorrect or missing functions
  • Interface errors
  • Errors in data structures or external database access
  • Behavior or performance errors
  • Initialization and termination errors

Advantages:

  • Well suited and efficient for large code segments.
  • Code Access not required.
  • Clearly separates user’s perspective from the developer’s perspective through visibly defined roles.
  • Large numbers of moderately skilled testers can test the application with no knowledge of implementation, programming language or operating systems.

 

Disadvantages:

  • Limited Coverage since only a selected number of test scenarios are actually performed.
  • Inefficient testing, due to the fact that the tester only has limited knowledge about an application.
  • Blind Coverage, since the tester cannot target specific code segments or error prone areas.
  • The test cases are difficult to design.

 

White Box testing: White Box Testing (also known as Clear Box Testing, Open Box Testing, Glass Box Testing, Transparent Box Testing, Code-Based Testing or Structural Testing) is a software testing method in which the internal structure/ design/ implementation of the item being tested is known to the tester. Programing and implementation knowledge is required to perform white box testing. The tester himself select input to test the parts of code and determine respective outputs.

White box testing involves the testing of the software code for the following:

  • Internal security holes
  • Broken or poorly structured paths in the coding processes
  • The flow of specific inputs through the code
  • Expected output
  • The functionality of conditional loops
  • Testing of each statement, object and function on an individual basis

Advantages:

As the tester has knowledge of the source code, it becomes very easy to find out which type of data can help in testing the application effectively.

  • It helps in optimizing the code.
  • Extra lines of code can be removed which can bring in hidden defects.
  • Due to the tester’s knowledge about the code, maximum coverage is attained during test scenario writing.

 

Disadvantages:

  • Due to the fact that a skilled tester is needed to perform white box testing, the costs are increased.
  • Sometimes it is impossible to look into every nook and corner to find out hidden errors that may create problems as many paths will go untested.
  • It is difficult to maintain white box testing as the use of specialized tools like code analysers and debugging tools are required.

 

Grey Box Testing: Grey Box Testing also known as Translucent Testing, is testing technique in which tester has limited knowledge about internal functionality of system. This technique involves the combination of white box and black box testing. Testers that use grey box testing need high-level application documentation to complete the tests. Grey box testing is geared toward finding defects based on improper structure or application use.

software_testing_methodology_2

Advantages:

  • Offers combined benefits of black box and white box testing wherever possible.
  • Grey box testers don’t rely on the source code; instead they rely on interface definition and functional specifications.
  • Based on the limited information available, a grey box tester can design excellent test scenarios especially around communication protocols and data type handling.
  • The test is done from the point of view of the user and not the designer.

 

Disadvantages:

  • Since the access to source code is not available, the ability to go over the code and test coverage is limited.
  • The tests can be redundant if the software designer has already run a test case.
  • Testing every possible input stream is unrealistic because it would take an unreasonable amount of time; therefore, many program paths will go untested.

 

 

Black Box Testing V/S White Box testing V/S Grey Box Testing:

software_testing_methodology_3

 

Comparison between the Three Testing Types

 

Black Box Testing Grey Box Testing White Box Testing
1 The Internal Workings of an application are not required to be known Somewhat knowledge of the internal workings are known Tester has full knowledge of the Internal workings of the application
2 Also known as closed box testing, data driven testing and functional testing Another term for grey box testing is translucent testing as the tester has limited knowledge of the insides of the application Also known as clear box testing, structural testing or code based testing
3 Performed by end users and also by testers and developers Performed by end users and also by testers and developers Normally done by testers and developer
4 Testing is based on external expectations, Internal behavior of the application is unknown Testing is done on the basis of high level database diagrams and data flow diagrams Internal workings are fully known and the tester can design test data accordingly
5 This is the least time consuming and exhaustive Partly time consuming and exhaustive The most exhaustive and time consuming type of testing
6 Not suited to algorithm testing Not suited to algorithm testing Suited for algorithm testing
7 This can only be done by trial and error method Data domains and Internal boundaries can be tested, if known Data domains and Internal boundaries can be better tested

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