Introduction to software testing potx

Introduction to
software testing
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Contents
 Definitions, Principles, Axioms
 Stages of testing
 Perspectives on Software Testing
 A little math (Part 1)
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Definitions, Principles, Axioms
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Definitions
 Testing
 Verification
 Validation
 Error/Defect
 Black box testing
 White box testing
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Definitions of Testing (1)
 The process of executing a program (or part
of a program) with the intention of finding
errors (Myers, Humphrey)
 The purpose of testing is to find errors.
Testing is the process of trying to discover
every conceivable fault or weakness in a
work product (Myers, Kit)
 The process of searching for errors (Kaner)
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Definitions of Testing (2)
 Testing – the process of finding errors and of

validating the program/system (Jorgensen)
 The purpose of software testing is to find
errors and to get them fixed (Bitzenhofer)
 The purpose of software testing is to reduce
risk (E&M)
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Verification and Validation:
Myers
 Verification: An attempt to find errors by
executing a program in a test or simulated
environment
 Validation: An attempt to find errors by
executing a program in a real environment
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Verification and Validation: IEEE
 Verification: The process of evaluating a
system or component to determine whether
the products…satisfy the conditions
imposed…
 Validation: The process of evaluating a
system or component…to determine whether
it satisfies specified requirements.
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Verification and Validation:
Kaner
 Verification: Checking a program against the
most closely related design documents or
specifications (“Design Verification Testing”)
 Validation: Checking the program against the
published user or system requirements

(“System Validation Testing”)
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Software Fault Terminology
 Error – a mistake in design, coding,
requirements, even testing
 Fault (defect) – the representation of the error
 Failure – what happens when the fault
“executes”
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Software Fault Terminology:
Examples
 Error
 A wrong loop index
 Programmer-to-device pointer error
 Fault – the representation of the error
 A loop executes one too many times
 A programmed parameter gets written to the wrong address
 Failure – what happens when the fault “executes”
 A table overflows; memory gets overwritten
 The physician only thinks he/she changed that heart parameter
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Black and White Box
 Black box testing
 Designed without knowledge of the program‟s
internal structure and design
 Based on functional requirements
 Also called Functional Testing
 White box testing
 Examines the internal design of the program
 Requires detailed knowledge of its structure

 Also called Structural Testing
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Six Essentials of Software
Testing (1)
1.The quality of the test process determines the
success of the test effort.
2.Prevent defect migration by using early life-
cycle testing techniques.
3.The time for software testing tools is now.
Adapted from Software Testing in the Real World, Edward Kit; Addison-
Wesley, 1995
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Six Essentials of Software
Testing (2)
4.A real person must take responsibility for
improving the testing process.
5.Testing is a professional discipline requiring
trained, skilled people.
6.Cultivate a positive team attitude of creative
destruction.
Adapted from Software Testing in the Real World, Edward Kit; Addison-
Wesley, 1995
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Some Principles and Axioms
of Testing (1)
 “Program testing can be used to show the
presence of bugs, but never their absence.”
(Dijkstra, 1969)
 One of the most difficult problems in testing is
knowing when to stop.

 It is impossible to test your own program.
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Some Principles and Axioms
of Testing (2)
 As the number of detected defects in a piece
of software increases, the probability of the
existence of more undetected defects also
increases.
 “Testing is an extremely creative and
intellectually challenging task” (Myers again)
 Exhaustive testing is impossible.
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Stages of testing
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The Test Process
 Requirements phase
 Planning phase
 Design and development phase
 Execution phase
 Reporting phase
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Software Test Execution
Stages
 Unit Test
 Design Verification Test (DVT)
 Interface, Integration, Exit/Formal
 System Validation Test (SVT)
 Main, Regression, Acceptance
 Customer Acceptance Test
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Unit Test
 Performed by the developers
 White-box testing
 Should be done with each release to testing
 Results should be communicated to the Test
Group
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Typical Entry Criteria (Unit
Test)
 Module compiles successfully (no errors,
approved warnings)
 Unit Test Plan complete
 Unit Test Cases complete
 Tools are available
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Typical Unit Test Activities
 Source level debugging if it won‟t compile
 Design and review the Unit Test cases
 Track test defects (maybe)
 Measure Unit Test coverage
 Make sure it builds
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Typical Exit Criteria (Unit Test)
 All tests attempted
 99% of the tests executed successfully
 85% statement coverage
 Test cases have been stored under
Configuration Management
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Software Test Stages

 Unit Test
 Design Verification Test
 Interface, Integration, Exit/Formal Test Phase
 System Validation Test
 Main, Regression, Acceptance
 Customer Acceptance Test
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Design Verification Test (DVT)
 Performed by the test organization
 Black box testing
 Verification of engineering requirements
 Verification of the software design