Unit 1 basic concepts of testing & quality

BASIC CONCEPT OF TESTING AND QUALITY
UNIT - 1
1
Prepared By: Ravi J Khimani, CSE Department, SLTIET, Rajkot

QUALITY REVOLUTION
 Quality – critical issue in product development
 In the past, near about 1940, Quality Revolution
began.
 Due to – Global Competition, OutSourcing, Off-
Shoring and increasing customer expectation.
 Developing quality product in tighter schedule is
big issue for companies.
2

QUALITY REVOLUTION
 In old approach, Efforts to improve quality is
centered around the end of product
development.
 In new approach, improve quality
encompasses all phases: from Requirement
Analysis to Final Delivery of Product.
3

QUALITY REVOLUTION
 An effective quality process must focus on:
 Paying attention to customer expectation
 Making efforts to continuously improve quality.
 Integrate measurement with design and
development.
 Develop system level perspectives with
concentrating on methodology and process.
 Eliminate waste through continuous improvement
4

QUALITY REVOLUTION
 Quality movement started around 1940-1950
 William Edward Deming, gives literature on
Statistical Quality Control (STQ)
 STQ is discipline based on measurements and
statistics.
 In which, decisions are made and plans
developed on the collection and evaluation of
facts and data.
5

QUALITY REVOLUTION
 Deming gave Shewhart Method for STQ.
 In which, he gave Plan – Do – Check – Act
(PDCA) cycle, also known as Shewhart Cycle.
6

QUALITY REVOLUTION
 Between 1950 – 1970, companies came up
with innovative principle, known as “Lean
Principle”.
 Which is, “A systematic approach to identify
and eliminate waste through continuous
improvement, flowing the product at the pull of
the customer expectations.”
 For Example, to compress the time period in
banking payments. 7

QUALITY REVOLUTION
 In the era of 1950, Joshep M Juran of US
proposed raising level of Quality Management
from Manufacture Dept. to overall
organization.
 That Quality Management is known as Total
Quality Control (TQC).
 It includes companywide activities, audits,
quality circle and promotions of quality 8

QUALITY REVOLUTION
 That TQC emphases on,
 Quality comes first not short-term profits.
 Customer comes first not the producers.
 Decisions are based on Data and Facts.
 Management is participatory and respectful of all
employees
 Management is driven by cross-functional committees
covering product planning, design, sales, marketing,
manufacturing, purchasing, distribution.
9

QUALITY REVOLUTION
 One of the TQC method
developed by Japan, is
known as Ishikawa OR
cause-and-effect
method.
 It says, product quality
comes from four
causes, materials, 10

QUALITY REVOLUTION
 Traditionally, the TQC and Lean Concept are
applied to Manufacturing Department.
 The software development process uses these
concepts through “Software Capability Maturity
Model (CMM)” model, to guide the production
of qualitative software.
 Which provides framework to discuss software
production issues.
11

SOFTWARE QUALITY
 What is Software Quality?
 Quality is a complex concept – means different things
to different people.
 Kitchenham and Pfleeger discuss software quality
in five different ways:
 Transcendental View:
 It envisages quality as something that can be recognized but
is difficult to define.
 It can be also applied to complex area of regular life.
 Not specific to only Software Quality.
12

SOFTWARE QUALITY
 User View:
 It perceives quality as fitness for purpose.
 Key question: “Does product satisfy user needs?”
 Manufacturing View:
 Here quality level is determined by considering product’s
specification.
 Product View:
 Quality is viewed as inherent characteristics. Like
Internal Characteristics, external characteristics.
13

SOFTWARE QUALITY
 Value Based View:
 Depends on amount a customer is willing to pay for it.
 In mid-1970, McCall, Richards and Walters
were gave the software quality in two terms,
 Quality Factors
 Quality Criteria
14

SOFTWARE QUALITY
 A quality Factor
 represents behavioral characteristics of system.
 For example, Correctness, Reliability, Efficiency,
Testability, Maintainability, Modularity and
Reusability.
 A Quality Criteria
 Is an attribute of Quality Factor that can be related
to Software Development.
15

SOFTWARE QUALITY
 There are various software quality models have
been proposed for Software Quality and its
related attributes
 Two most popular models are
 CMM [Software Capability Maturity Model]
 ISO [International Standard Organization]
 In the field of Testing two popular models are
available,
 TPI [Test Process Improvement]
 TMM [Test Maturity Model]
16

FAILURE, FAULT, ERROR AND DEFECT
 In software testing, we can find references to
these four terms.
 In fault – tolerant computing community,
 Failure: A failure is said to occur whenever the
external behaviour of a system does not confirm to that
prescribed in the system speciﬁcation.
 Error: An error is a state of the system. In the absence
of any corrective action by the system, an error state
could lead to a failure which would not be attributed to
any event subsequent to the error.
17

 Fault: A fault is the adjudged (true) cause of an
error.
 A fault may remain undetected for a long time,
until some event activates it.
 When an event activates a fault,
 it brings the program into an intermediate error
state.
 If computation is allowed to proceed from an error
18

 in fault-tolerant computing, corrective actions
can be taken to take a program out of an error
state into a desirable state such that subsequent
computation does not eventually lead to a
failure.
 The process of failure manifestation can
therefore be succinctly represented as a
behaviour chain as follows:
19

 In software, a system may be defective due
to design issues; certain system states will
expose a defect, resulting in the development
of faults are defined as incorrect signal values
or decisions within the system.
 In practical purpose, both term, Defect and
Fault are synonymous terms.
20

 For Example,
Consider a small organization. Defects in the
organization’s staff promotion policies can cause
improper promotions, viewed as faults. The resulting
ineptitudes & dissatisfactions are errors in the
organization’s state. The organization’s personnel or
departments probably begin to malfunction as result
of the errors, in turn causing an overall degradation of
performance. The end result can be the organization’s
failure to achieve its goal.
21

ROLE OF TESTING
 Testing plays an important role in achieving
and assessing the quality of a software
product .
 we can improve the quality of the products as
we repeat a test - find defects – fix cycle
during development.
 But how can we perform system level tests
before releasing product? 22

ROLE OF TESTING
 Friedman and Voas say, “software testing is a
verification process for software quality
assessment and improvement.”
 Software quality assessment is divided into
two categories,
 Static Analysis
 Dynamic Analysis
23

1. STATIC ANALYSIS [ROLE OF TESTING]
 It is based on the examination of a number of documents,
 requirements documents,
 software models,
 design documents
 source code.
 It also includes code review, inspection, walk-through,
algorithm analysis, and proof of correctness.
 It does not involve actual execution of the code under
development.
 Instead, it examines code and reasons over all possible
behaviours that might arise during run time.
 For Ex., Compiler optimizations are standard static analysis.24

2. DYNAMIC ANALYSIS [ROLE OF TESTING]
 It involves actual program execution with input values.
 During execution, it observes the behavioural and
performance properties of the program.
 For practical considerations, a finite subset of the input
set can be selected.
 Therefore, in testing, we observe program behaviours
and reach a conclusion about the quality of the system.
 Careful selection of a finite test set is crucial to reaching
a reliable conclusion.
25

ROLE OF TESTING [CONT…]
 Both Analysis techniques are complementary
in nature, and for better effectiveness, both
must be performed repeatedly and alternated.
 Practitioners and researchers need to remove
the boundaries between static and dynamic
analysis and create a hybrid analysis that
combines the strengths of both approaches
26

OBJECTIVES OF TESTING
 The stakeholders in a test process are the
programmers, the test engineers, the project
managers, and the customers.
 A stakeholder is a person or an organization
who influences a system’s behaviours or who
is impacted by that system.
 Different stakeholders view a test process from
different perspectives, as follows,
27

 It does work:
 While implementing a program unit, the programmer may
want to test whether or not the unit works in normal
circumstances.
 The programmer gets much confidence if the unit works to his
or her satisfaction.
 The same idea applies to an entire system as well—once a
system has been integrated, the developers may want to test
whether or not the system performs the basic functions.
 Here, for the psychological reason, the objective of testing is
to show that the system works, rather than it does not work.
28

 It does not work:
 Once the programmer (or the development team) is satisﬁed
that a unit (or the system) works to a certain degree, more
tests are conducted with the objective of finding faults in the
unit (or the system).
 Here, the idea is to try to make the unit (or the system) fail.
 Reduce the risk of failure:
 Software systems contain faults, which cause the system to
fail.
 “failing from time to time” gives rise of failure rate.
 As faults are discovered and fixed during more tests,
 Thus, a higher level objective of performing tests is to bring29

 Reduce the cost of testing:
 The different kinds of costs associated with a test process
include
 the cost of designing, maintaining, and executing test cases,
 the cost of analyzing the result of executing each test case,
 the cost of documenting the test cases,
 and the cost of actually executing the system and documenting it.
 Therefore, the less the number of test cases designed, the
less will be the associated cost of testing.
 However, producing a small number of arbitrary test cases is
not a good way of saving cost.
 Objective – more test cases – more reliable software.
 Its define effectiveness of test cases.
30

TEST CASE
 Basic Form, it’s a pair of,
<input, expected outcome>
 In stateless system, outcome depends only on the
current input.
 For example, calculate square root of number,
 A compiler for C language.
31

TEST CASE
 In state-oriented system, outcome depends on
current input as well as current state of system.
 For this test case consists of Sequence of <input,
expected outcome> pairs, according to state.
 It also consists of Decision and Timing factor.
 For example, ATM Machine,
32

EXPECTED OUTCOME
 Outcome of program execution is complex entity,
which includes,
 Value produced
 State change (program or database)
 Set of values interpreted together for valid outcome.
 ORACLE: is important concept of Test Design.
 Oracle is entity – Program, Process, Human
Expert or body of data – that tells us the expected
outcome of test. 33

EXPECTED OUTCOME
 Expected Outcome should be computed while
designing test cases.
 Before program execution and with selected
inputs.
 Will eliminate implementation biasing.
 The process is of – execute program –
observe actual output – verify actual output –
use that verified output in subsequent test
34

CONCEPT OF COMPLETE TESTING
 It means “there are no undiscoverable faults at the end of
test phase”.
 It’s near impossible, due to
 Input domain is to large
 Program may have large number of state based on valid and
invalid inputs.
 Timing constraint
 Design (for program) issues too complex
 Impossible to create all possible execution environments like
weather, temperature, altitude, pressure, etc…
 “Input value which is valid but is not property timed is
called inopportune Input”.
35

CENTRAL ISSUE IN TESTING
 Impossible to test complete input domain to
discover faults.
 Select subset of Domain is best thing to test
program.
36

TEST ACTIVITIES
 Identify objective to be tested
 Clear purpose must be associated with every test
case.
 Select Inputs
 Based on specification, source code and
expectation
 Compute the expected outcome
 Can be done from high-level understanding of the38

TEST ACTIVITIES
 Set up execution environment of program
 Prepare right execution environment
 For ex, Initialize local system, external to program like
making network connection, right database system
available.
 For ex, Initialize any remote, external system like
distributed system to run client code.
 Execute the Program
 With selected input and observe actual output.
 Test Coordination concept is used in synchronizing
different components of Test Cases, like different
physical location. 39

TEST ACTIVITIES
 Analyze Test Result
 Comparison should be precise.
 After analyzing, Test Verdicts should be assigned,
like Pass, Fail, inconclusive.
 Test Report must be written, contains
reasons of failure of test cases
analysis of failure
A indication to actual outcome, test case,
input values tested, environment of 40

VERIFICATION AND VALIDATION
 Two similar concept
 Verification
 Determine that product of given development
phase satisfies the requirements established
before starting of that phase.
 Like requirement specification, design
specification, code, user manual.
 “Activities that check the correctness of a
development phase are called Verification
41

VERIFICATION AND VALIDATION
 Validation
 Activities that determine and confirm that product
meets its desired use.
 Aim at confirming that product meets user’s
expectations.
 Focus on final product.
 Should be executed at early stage of development
cycle, not at the end of development cycle.
42

VERIFICATION VS. VALIDATION
Verification Validation
Confirming that Building product
correctly
Confirming that building correct
product
Review interim works like
specification, design specification,
code, user manual.
Is performed at the end of
development phase of each part of
system.
Verification considers quality attributes
like consistency, correctness,
completeness.
Validation considers only correctness
and satisfaction.
Can be applied through Statistic
Analysis Techniques like inspection,
walkthrough, reviews, checklists,
Can be applied by running system in
its actual environment using verity of
Tests.
43

CORRECTNESS
 Correctness from software engineering
perspective can be defined as the stickiness to
the specifications that determine how users
can interact with the software and how the
software should be have when it is used
correctly.
 If the software behaves incorrectly, it might
take considerable amount of time to achieve.44

CORRECTNESS
 Below are some of the important rules for effective
programming which are consequences of the program
correctness theory.
 Defining the problem completely.
 Develop the algorithm and then the program logic.
 Reuse the proved models as much as possible.
 Prove the correctness of algorithms during the design
phase.
 Developers should pay attention to the clarity and simplicity
of your program.
 Verifying each part of a program as soon as it is developed.45

SOURCES OF INFORMATION FOR TEST CASES
 A software development process generates a large
body of information, such as requirements speciﬁcation,
design document, and source code.
 In order to generate effective tests at a lower cost, test
designers analyze the following sources of information:
 Requirements and functional specifications.
 Source code
 Input and output domains
 Operational Profiles
 Fault model [Error Guessing, Fault Seeding, Mutation
46

TEST LEVELS
 Performed at different levels involving
complete system.
 Software goes through four stages: Unit,
Integration, System and Acceptance level
testing.
 First three inside developing organization
 Last one is outside developing organization
 These four stages of testing is known as V- 47

CONTROL FLOW GRAPH
 It’s a graphical representation of program unit.
 Three symbols are used.
49

CONTROL FLOW GRAPH
 A rectangle represents sequential computation.
 A diamond box represents decision point.
 Two branches one decision box has, True or False.
 A small circle represents a merge point.
 We are not labeling merge point.
50

TESTING TYPES
 Black Box Testing
 Black-box testing is a method of software testing that
examines the functionality of an application based on the
specifications. It is also known as Specifications based
testing.
 Independent Testing Team usually performs this type of testing
during the software testing life cycle.
 This method of test can be applied to each and every level of
software testing.
 There are different techniques involved in Black Box testing,
 like Equivalence Class, Boundary Value Analysis, Domain
Tests, Orthogonal Arrays, Decision Tables, State Models, All-51

TESTING TYPES
 White Box Testing
 White box testing is a testing technique, that examines the program
structure and derives test data from the program logic/code. The other
names of white box testing are clear box testing, open box testing, logic
driven testing or path driven testing or structural testing.
 White Box Testing Techniques:
 Statement Coverage - This technique is aimed at exercising all programming
statements with minimal tests.
 Branch Coverage - This technique is running a series of tests to ensure that all
branches are tested at least once.
 Path Coverage - This technique corresponds to testing all possible paths which
means that each statement and branch is covered.
52

TESTING TYPES
 Model Based Testing
 Model-based testing is a software testing technique in which the
test cases are derived from a model that describes the functional
aspects of the system under test.
 It makes use of a model to generate tests that includes both
offline and online testing.
 Importance
 Unit testing wont be sufficient to check the functionalities
 To ensure that the system is behaving in the same sequence of actions.
 Model-based testing technique has been adopted as an integrated part
of the testing process.
 Commercial tools are developed to support model-based testing. 53

TESTING TYPES
 Interface Testing
 Interface Testing is performed to evaluate whether systems or components
pass data and control correctly to one another. It is to verify if all the
interactions between these modules are working properly and errors are
handled properly.
 Verify that communication between the systems are done correctly
 Verify if all supported hardware/software has been tested
 Verify if all linked documents be supported/opened on all platforms
 Verify the security requirements or encryption while communication happens
between systems
 Check if a Solution can handle network failures between Web site and
application serve 54

TESTING TYPES
 Unit Testing
 Tests individual program units like function, class
 After surety of units working properly, modules are
assembled to larger subsystem.
 By Software Developer.
 Integration Testing
 Performed on assembled units of system in unit
testing.
 By Software Developer and Integration test
55

TESTING TYPES
 System Testing
 Object is to construct a reasonably stable system that
can withstand to System-Level Testing.
 System level testing includes functionality testing,
security testing, reliability testing, stability, stress,
performance, load testing.
 Aim to discover most of the faults and verify fixes are
working.
 System testing composed of create test plan, design
test suit, prepare test environments, executing tests.
56

TESTING TYPES
 Regression Testing
 Perform throughout life cycle of system
development.
 Performed when component of system is modified.
 Idea to verify that modification does not affect
existing work and does not introduce new faults.
 It is distinct level of testing
 Sub-phase of unit, integration and system-level
testing. 57

TESTING TYPES
 Acceptance Testing
 After completion of all above testing, product is
delivered to customer.
 Customer performs their own series of tests, called
acceptance tests.
 Objective of this testing to measure Quality of
Product.
 Key notion is customer’s expectations from the
system.
58

TESTING TYPES
 Two kinds of Acceptance Testing
 User Acceptance Testing (UAT): done by user to ensure
system performs contractual acceptance criteria.
 Business Acceptance Testing (BAT): done by supplier’s
development organization, to ensure that system will
pass UAT.
59

Unit 1 basic concepts of testing & quality

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Unit 1 basic concepts of testing & quality