Software is incorporated with other system elements (e.g., hardware, people, information), and a series of system integration and validation tests are conducted. These tests fall outside the scope of the software process and are not conducted solely by software engineers. A classic system testing problem is "finger-pointing." This occurs when an error is uncovered, and each system element developer blames the other for the problem. Rather than indulging in such nonsense, the software engineer should anticipate potential interfacing problems.

(1) Design error-handling paths that test all information coming from other elements of the system.

(2) Conduct a series of tests that simulate bad data or other potential errors at the software interface.

(3) Record the results of tests to use as "evidence" if finger-pointing does occur.

(4) Participate in planning and design of system tests to ensure that software is adequately tested.

Recovery Testing:-

Many computer based systems must recover from faults and resume processing with in a specified time. In some cases, a system must be fault tolerant; that is, processing faults must not cause overall system function to cease. In other cases, a system failure must be corrected within a specified period of time or severe economic damage will occur.

It is a test that forces the software to fail in a variety of ways and verifies that recovery is properly performed. If recovery is automatic (performed by the system itself), reinitialization, check pointing mechanisms, data recovery, and restart are evaluated for correctness. If recovery requires human intervention, the mean-time-to-repair (MTTR) is evaluated to determine whether it is within acceptable limits.

Security Testing:-

Any computer-based system that manages sensitive information or causes actions that can improperly harm (or benefit) individuals is a target for improper or illegal penetration. Penetration spans a broad range of activities: hackers who attempt to penetrate systems for sport; disgruntled employees who attempt to penetrate for revenge; dishonest individuals who attempt to penetrate for illicit personal gain.

Security testing attempts to verify that protection mechanisms built into a system will, in fact, protect it from improper penetration. "The system's security must, of course, be tested for invulnerability from frontal attack—but must also be tested for invulnerability from rear attack."

During security testing, the tester plays the role(s) of the individual who desires to penetrate the system. Anything goes! The tester may attempt to acquire passwords through external means; may attack the system with custom software designed to breakdown any defences that have been constructed; may overwhelm the system, thereby denying service to others; may purposely cause system errors, hoping to penetrate during recovery.

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

(1) Special tests may be designed that generate ten interrupts per second, when one or two is the average rate.

(2) Input data rates may be increased by an order of magnitude to determine how input functions will respond.

(3) Test cases that require maximum memory or other resources are executed.

(4) Test cases that may cause thrashing in a virtual operating system are designed.

(5) Test cases that may cause excessive hunting for disk-resident data are created.

Performance Testing:-

For real-time and embedded systems, software that provides required function but does not conform to performance requirements is unacceptable. Performance testing is designed to test the run-time performance of software within the context of an integrated system. Performance testing occurs throughout all steps in the testing process.