Introduction to Software Testing

What is Software Testing?

• Software testing is an investigation conducted to provide stakeholders with information about the quality of the product or service under test.
• (IEEE) - Software testing is the process of analyzing a software item to detect the differences between existing and required conditions (that is, bugs) and to evaluate the features of the software item.
• Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software implementation. Test techniques include, but are not limited to, the process of executing a program or application with the intent of finding software bugs (errors or other defects).
• Software testing is a process used to identify the correctness, completeness, and quality of developed computer software.
• Software testing can be stated as the process of validating and verifying that a computer program/application/product:

             o meets the requirements that guided its design and development,

             o works as expected,

             o can be implemented with the same characteristics,and

             o satisfies the needs of stakeholders.

Software testing, depending on the testing method employed, can be implemented at any time in the development process. Traditionally most of the test effort occurs after the requirements have been defined and the coding process has been completed, but in the Agile approaches most of the test effort is on-going. As such, the methodology of the test is governed by the chosen software development methodology.

Testing can never completely identify all the defects within software. Instead, it furnishes a criticism or comparison that compares the state and behavior of the product against oracles—principles or mechanisms by which someone might recognize a problem. These oracles may include (but are not limited to) specifications, contracts, comparable products, past versions of the same product, inferences about intended or expected purpose, user or customer expectations, relevant standards, applicable laws, or other criteria.

A primary purpose of testing is to detect software failures so that defects may be discovered and corrected. Testing cannot establish that a product functions properly under all conditions but can only establish that it does not function properly under specific conditions. 

The scope of software testing often includes examination of code as well as execution of that code in various environments and conditions as well as examining the aspects of code: does it do what it is supposed to do and do what it needs to do. 

In the current culture of software development, a testing organization may be separate from the development team. There are various roles for testing team members. Information derived from software testing may be used to correct the process by which software is developed.


Testing includes a set of activities conducted with the intent of finding errors in software so that it could be corrected before the product is released to the end users.

software testing is an activity to check whether the actual results match the expected results and to ensure that the software system is defect free.

Importance of Testing: 

• This isChinaAirlines Airbus A300 crashing due to a software bug on April 26, 1994 killing 264 innocent lives
• Software bugs can potentially cause monetary and human loss, history is full of such examples
• In 1985,Canada's Therac-25 radiation therapy machine malfunctioned due to software bug and delivered lethal radiation doses to patients ,leaving 3 people dead and critically injuring 3 others
• In April of 1999 ,a software bug caused the failure of a $1.2 billion military satellite launch, the costliest accident in history
• In may of 1996, a software bug caused the bank accounts of 823 customers of a major U.S. bank to be credited with 920 million US dollars
• As you see, testing is important because software bugs could be expensive or even dangerous