Software Testing What is Testing?

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.
TERMINOLOGIES
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
A program requires two 8 bit integers as
inputs, so total possible combinations are:
inputs, so total possible combinations are:


2
2
8
8
x 2
x 2
8
8


If one second is required to execute one set
If one second is required to execute one set
of inputs, it will take 18 hours.
of inputs, it will take 18 hours.
Example 2


Suppose we have a program which uses loop
Suppose we have a program which uses loop
and If statement as following:
and If statement as following:



The number of paths in
The number of paths in
the example is 10
the example is 10
14
14


If only 1 minute is require
If only 1 minute is require
to test one path, it may
to test one path, it may
take 1/5 billion years
take 1/5 billion years
to execute all path.
to execute all path.
<=20 times