Monday, September 24, 2012

Difference between Bug, Defect and Error

Bug, Defect and Error
An Error found in the development environment before the product is shipped to the customer.
Bug: Simply Bug is an error found BEFORE the application goes into production. A programming error that causes a program to work poorly, produce incorrect results, or crash.  An error in software or hardware that causes a program to malfunction.

Defect is the difference between expected and actual result in the context of testing. Defect is the deviation of the customer requirement. An Error found in the product itself after it is shipped to the customer. Defect is an error found AFTER the application goes into production. Simply defect can be defined as a variance between expected and actual. Defect is an error found AFTER the application goes into production.

Categories of defects - There are three main category of defects;
Wrong: The requirements have been implement the wrong way. This defect is a variance from the given specification.

Missing: There was a requirement given by the client and it was not done. This is a variance from the specifications, an indication that a specification was not implemented, or a requirement of the customer was not noted correctly.

Bug, Defect and Error
  Extra: A requirement incorporated into the product that was not given by the end   customer. This is always a variance from the specification, but may be an attribute  desired by the user of the product. However, it is considered a defect because it’s  a variance from the existing requirements.

  Error: It the one which is generated because of wrong login, loop or due to syntax. Error means normally arises in software Error means to change the functionality of the program.

Fault: A wrong or mistaken step, process or Data definition in a computed program which causes the program to perform in an unintended or unanticipated manner.

Difference between a defect and a failure -
When a defect reaches the end customer it is called a failure and if the defect is detected internally and resolved it’s called a defect.


  1. “A mistake in coding is called error ,error found by tester is called defect, defect accepted by development team then it is called bug ,build does not meet the requirements then it Is failure.

  2. really a neat and clear answer STEBIN

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  4. please update your definition as people will learn the wrong definition as mentioned by you.. non-production errors too are defects. Any identified bug or non-conformance to requirement is a defect.Production defects are the isues that have gone to the end user without getting identified earlier.


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