Software Testing What is Testing?

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

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

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

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

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

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

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 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

<=20 times