Software Testing What is Testing?  Testing is the process of demonstrating that errors are not present  The purpose of testing is to show that a program performs its intended functions correctly  Testing is the process of establishing confidence that a program does what it is suppose to do. These definitions are incorrect. Why??? “Testing is the process of executing a program with the intent of finding errors” Why should We Test?  Although Software Testing is an expensive activity. However, if we produce a software product without Testing may lead to cost potentially much higher than of testing  “Life Critical System”, economics must not be the prime consideration while deciding whether a product should be released to a customer.  In commercial system it is often difficult to estimate the cost of errors. Who should Do the Testing?  It is very difficult for software developer to point out errors from own creations(Why?)  Testing persons are different from Development persons for the overall benefit of the system  Developers provide guide lines during testing  Whole responsibility is owned by Testing persons What should We Test?  It is not possible to test the software for all possible combination of input cases (example)  It is impossible to execute all path the program (example) Complete Testing is impossible, although we may wish to do so.  Organizations should develop strategies and policies for choosing effective testing techniques TERMINOLOGIES Error, Mistake, Bug, Fault and Failure  Error: People make errors. A good synonym is MISTAKE. Mistakes during coding is called Bug  Fault: An error may lead to one or more faults. Fault is the representation of error. Defect is a good synonym for fault  Failure: occurs when a fault executes. One fault may lead to many Failures TERMINOLOGIES Test, Test Case, Test Suite  A Test: is the act of exercising software with test cases. There are two distinct goals of a test: either to find failures, or to demonstrate correct execution. TERMINOLOGIES Test, Test Case, Test Suite  Test Case: Describes an input description and an expected output description (example)  A Good Test Case has high probability of finding an error  The main objective of Test Case Designer is to identify good test cases  Test Suite: the set of test cases. Any combination of test cases may generate a Test Suite TERMINOLOGIES Verification and Validation  Verification: the process of conforming that software meets its specification (Checking the software with respect to specification)  Validation: the process of conforming that software meets the customer’s requirements (Checking the software with respect to customer’s expectation)  If there is a gap at RSR level that will only be know during validation activities  Poor understand of expectation may lead to incorrect specifications TERMINOLOGIES Alpha, Beta and Acceptance Testing  Alpha and Beta Testing: used when the software developed as a product for anonymous customers.  Alpha tests are conducted at developer’s site by customer. This test may be stared when formal testing process near completion  Beta tests are conducted by the customers/end users at their site. Beta testing is conducted in a real environment that cannot be control by the developer. [...]... Alpha, Beta and Acceptance Testing  Acceptance Testing: used when the software is developed for a specific customer  A series of test are conducted to enable the customer to validate all requirements These test are conducted by the end user/customer Example 1  A program requires two 8 bit integers as inputs, so total possible combinations are:   28 x 28 If one second is required to execute one... is required to execute one set of inputs, it will take 18 hours Example 2    Suppose we have a program which uses loop and If statement as following: The number of paths in the example is 1014 If only 1 minute is require to test one path, it may take 1/5 billion years to execute all path