Software Testing Strategies- continued.....

Validation Testing

At the culmination of integration testing, software is completely assembled as a package, interfacing errors have been uncovered and corrected, and a final series of software tests-validation testing-may begin. Validation can be defined in many ways, but a simple definition is that validation succeeds when software functions in a manner that can be reasonably expected by the customer. Software validation is achieved through a series of black box tests that demonstrate conformity with the requirements. A test plan outlines the classes of tests to be conducted and a test procedure defines specific test cases that will be used to demonstrate conformity with requirements. Both the plan and procedure are designed to ensure that all functional requirements are satisfied, all behavioral characteristics are achieved, all performance requirements are attained, documentation is correct, and human engineered and other requirements are met.

Stress Testing

During earlier software testing steps, white-box and black-box techniques resulted in thorough evaluation of normal program functions and performance Stress tests are designed to confront programs with abnormal situations In essence, the tester who performs stress testing asks "How high can we crank this up before it fails?"
Stress testing executes a system in a manner that demands resources in abnormal quantity, frequency, or volume. For example,

• special tests may be designed that generate ten interrupts per second, when one or two is the average rate
• input data rates may be increased by an order of magnitude to determine how input functions will respond
• test cases that require maximum memory or other resources are executed
• test cases that may cause thrashing in a virtual operating system are designed
  test cases that may cause excessive hunting for disk-resident data are created Essentially, the tester attempts to break the program