introduction to testing security testing ensures that access to the system is controlled appropriately given the requirements for examplefor an online shopping system there may be different security requirements depending upon whether you are browsing the storepurchasing some products or maintaining the product catalogue usability testing which may be performed by specialist usability group and may involved filming users while they use the system system testing validates that the system as whole actually meets the user requirements and conforms to required application integrity user acceptance testing is form of user oriented testing where users confirm that the system does and behaves in the way they expect installationdeployment and upgrade testing these three types of testing validate that system can be installed and deployed appropriate including any upgrade processes that may be required smoke tests used to check that the core elements of large system operate correctly they can typically be run quickly and in faction of the time taken to run the full system tests key testing approaches are discussed in the remainder of this section unit testing unit can be as small as single function or as large as subsystem but typically is classobjectself-contained library (apior web page by looking at small self-contained component an extensive set of tests can be developed to exercise the defined requirements and functionality of the unit unit testing typically follows white box approach(also called glass box or structural testing)where the testing utilizes knowledge and understanding of the code and its structurerather than just its interface (which is known as the black box approachin white box testingtest coverage is measured by the number of code paths that have been tested the goal in unit testing is to provide coverageto exercise every instructionall sides of each logical branchall called objectshandling of all data structuresnormal and abnormal termination of all loops etc of course this may not always be possible but it is goal that should be aimed for many automated test tools will include code coverage measure so that you are aware of how much of your code has been exercised by any given set of tests unit testing is almost always automated--there are many tools to help with thisperhaps the best-known being the xunit family of test frameworks such as junit for java and pyunit for python the framework allows developers tofocus on testing the unitsimulate data or results from calling another unit (representative good and bad results)