Ch1_A Perspective on Testing

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Ch. 1 A Perspective on Testing

Definitions and Concepts of Testing and Quality

What is

Testing?

What is

Quality ?

HowRelated?

1. Does finding a Lot of Problems through testing improveQuality? Ch. 1 A Perspective on Testing -

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Introduction to Testing Software Testing is a relatively new discipline although

programmers always debugged their programs.

Testing was conducted to show that software works.

In the 1970s Glen Myers wrote a book, Art ofSoftware Testing (1978).

He believed that the main purpose of testing is to findfaults.

Are these (works .vs. faults) opposing views?

2. Why do we and why should we Test ?Ch. 1 A Perspective on Testing -

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Why Test ?

Because we cant assume that the software works

How do we answer the question:Does this software work?

Is it reliable ? (system is continuously functioning > 720hrs) Is it functional ?

Complete Consistent

Is it responsive ? (response time < 1 second)

In general, what is the Quality of our software?

How do we answer this?

3. How would you answer this about the program that you wrote?How would you answer this about the program your friend wrote?

Ch. 1 A Perspective on Testing -

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Quality of Software?

Depends on what we include as software

Just the executable code ----- How about ?

the pre-populated data in the database

the help text and error messages

the source logic code

the design document

the test scenarios and test results

the reference manuals

the requirements document

When we talk about quality how much of the above(do we / should we) include?

How would you test these different artifacts?


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Approaches to ---Testing Software

Some of us hope that our software works as

opposed to ensuring that our software works?Why? Just foolish

Lazy

Believe that its too costly (time, resource, effort, etc.)

Lack of knowledge

DO NOT use the I feel lucky or I feel confident approachto testing - - - - although you may feel that way sometimes.

Use a methodical approach to testing to back up the

I feel lucky/confident feeling

Methods and metrics utilized must show VALUE Value, unfortunately, often are expressed in negative terms

Severe problems that cost loss of lives or business

Problems that cost more than testing expenses and effort5


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3 major Testing approaches

1. Traditionally, testing includes executing the code with test cases.

(assuming - code is the main software artifact)

2. What do we do with the non-executable software artifacts?

Reviews and Inspections

- Expensive in terms of human resources- A lot to maintain and keep updated

3. Can we provethat the software works or is defect free?

- Theoretically, given an arbitrary program we can not show that it has nobug.

- We can use Formal Proofs to show the behavior of code

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An Informal Survey in the 90s Professionals taking a course in testing:

60% were new to testing 20% had 1 to 5 years of experience in testing 20 % expert testers

Metric used in testing a) Most regularly used: Counting bugs found and ranking them by

severity b) Small number used : bug find rate or bug fix rate

Formal Methods used Almost none formally trained in inspection or analysis

Test tool: 76 % had been exposed to some automated test tool

Test definitions Most of the practicing testers could not supply good definitions of

testing terms; they just did the work!Ch. 1 A Perspective on Testing -

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Historical Progression of Attitudes onSoftware Quality

-PC and Desktop Computingbecame ubiquitous-multiple vendors-quicker product development &shorter term investment-systems ran by non-computerindividuals

1990s

**New product was fashionable

& reboot became acceptable.**

-Web availability to many-Business conducted on the Web

-Software and systems are nothobbies but a business again

Late 1990s & 2000s

**Product Reliability & Qualityis once again important** --

especially SECURITY--

-Large Host & Centralized

Systems-Single Vendor (hdw-sw-serv)-Long term development andlong term investment(10 yrs)-Single platform-Systems ran by computerprofessionals

1980s & Before

**Product Reliability & Qualitywas required and expected**

Even though we didntget good quality


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Current State (2000-2010s) on Testing

1. Software is written by many with the

entrepreneurial spirit: Speed to market New & innovation is treasured Small organization that cant afford much more than

coders

2. Embracing Agile process and mistaking it as fastproduction regardless of what:

Not much documented (requirements/design) Hard to test without documented material

3. Lack of Trained/Good/Experienced Testers Testers are not quite rewarded as equals to designers,but definitely gaining on and sometimes surpassingprogrammers(takes good cops to catch the thieves)

4. Improvement in tools and standards makingdevelopment easier and less error prone

Why ?

How ?Ch. 1 A Perspective on Testing -

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Is Quality still an Issue, today?

What is Quality?

Some common comments:

I know it when I see it

ReliableMeets requirements

Fit for use

Easy to use

ResponsiveFull function / full feature

Classy and luxurious

How would you define quality?Ch. 1 A Perspective on Testing -

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Some U.S. pioneers on Quality

Pioneers:Joseph M. Juran

Quality =>Fitness for use

W. Edward Deming Quality => Non-faulty system

More recently: Philip Crosby

Quality => conformance with requirements Achieve quality via prevention of error

Target of Quality is zero defect

Measure success via cost of qualityCh. 1 A Perspective on Testing -

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ISO/IEC 9126 (1994) Quality model

Quality is composed of severalcharacteristics:

FunctionalityReliabilityUsabilityEfficiencyMaintainability

Portability

How do you know if it is achieved & how would you test for these?Do these have to be specified in the requirements? ---- if they arenot-------- do we ask for these during review/inspection?

What do these mean ?


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Quality

Quality is a characteristic or attribute

Needs to be clearly defined and agreed to

May have sub-attributes (e.g. previous page)

Needs specific metrics for each of the sub-attributesNeeds to be measured with the defined metric(s)

Needs to be tracked and analyzed

Needs to be projected

Needs to be controlled

Testing and Measurement are two keyactivities that would help us manage quality.

Explain ----- the relationship ?

Imagine what it is likewithout this.


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Summarizing major Competitors to Quality

Schedule (first to market)

Requirements (bad or missing)

New and Exciting (demands of WANT not need)

Price and Availability (retail customers)


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Some Precept Concerning Quality & QA Quality requirements Does Not always dictate schedule !

Market Conditionoftendictates schedule (especially for smallcompanies)

BUT For large and multiple release software, quality is still a factor and may

affect schedule ---- albeit schedule is seldomly changed for quality Software development process today incorporates both the need for

speed and quality (incorporating the notion of ) a) service cost and b) rewrite for a replacement new product.

Quality does not require zero defect Reliability

Commercial (non-life critical or mission critical) products are notdeveloped with zero defect goal in mind. They are much more marketdriven --- market prefers but does not demand zero defects.

Focus on proper support Focus on main functions and heavily used areas (not all defects are the same) Focus on customer productivity (e.g. easy to learn and use) Zero Defect is very expensive proposition ( time & resource)Ch. 1 A Perspective on Testing -

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Users Do Not Always Know What

They Want Users may not know all the requirements (especially for large,

complex systems which require professional or legalknowledge.)

Users may not have the time or interest to really focus on

the requirements at the time when asked (timing problem).Users have their own fulltime jobs.

Users may not know how to prioritize needs from wishes

Users may not know how to articulate clearly all therequirements. (They are non-software development people.)

Developers may not listen well or properly interpret the usersstatements. (They are not industry specialists.)

Requirements is a key factor in software development ---- why?How does it affect software quality? ----- think about definitions of Quality--- meets requirements


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Requirements are not always Clear,

Stable, and Doable Not all requirements are technically feasible; sometimes the

desired new technology needs to be prototyped first.

Sometimes the requirements are changed, causing re-design or re-code without proper assessment of schedule

impact. Requirements are not always reviewed and signed off, but

sometimes given in verbal form --- especially small changes.

People mistake iterative development to mean continuouschange of requirements.

Whats the danger here? cost, schedule, quality


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Customers often go for New and

Exciting Product If the product has all the needed features it would sell ---

is not necessarily true; people often WANTnew & extrafeatures.

Reliability is not always enough; sometimes customers willsacrifice quality for new and exciting features.

The story of IBM OS/2 operating system and Microsofts DOSoperating system (even though both was commissioned byIBM).

IBM went for Reliability of the old Host Machines for desktop PCs

Microsoft went for exciting individual user interfaces

Over-emphasis of exciting features is one reason why weare regressing a little in software quality in the last ten years !

**Still, consider Apple i-phone success in spite of its activation & other problemsCh. 1 A Perspective on Testing -

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Price and Availability is sometimesmore important to customers

(especially for commodity levelsoftware) than Product Maturity orQuality.

At the commodity level software, the customers are

individuals who wants the product NOW at an competitiveprice. (much like shopping for a home appliance such as acoffee maker, T.V. or an i-phone)

Sophisticated and full feature software needs to bebalanced and sometimes traded off for price and speed.

Customers dont always need all the functions andproduct maturity they think they require ---- if the price isright!


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Summarizing: majorCompetitors and Adversaries

to Qualitywhen developing software

Schedule (first to market)

Requirements (bad or missing)

New and Exciting (demands of WANTnot need)

Price and Availability (retail customers)


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Start of Quality Assurance

As software size and complexity increased in the1960s and 1970s, many software projects started tofail.

Many software did not perform the required functions Others had performance (speed) problems

Some had large number of defects that prevented users fromcompleting their work; some just flat out wont even install !

Software Quality Crisis was recognized and QualityAssurance was born, along with the term SoftwareEngineering (1968 NATO conference).


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Software Quality Assurance (QA)

Software QA focused on 2 main areas

Software productSoftware process

The focus on the process areas borrowedmany techniques from the traditionalmanufacturing area

Concept of reliability (number of defects, mean timeto failure, probability of failure, etc. metrics)

Concept of process control in terms of looking atrepeatability of process--- repeatable processproduces similar product (or controllable results).

emphasis today : e.g. CMM & CMMI


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QA, Process Control, and Documentation

A period of heavy emphasis on softwaredevelopment process and excessivedocumentation dominated QA --- initially thisimproved the software crisis.

1. Process included multiple steps of reviews2. Process included multiple steps of testpreparation,

testing, and test result analysis3. Process was controlled by many documentsand

document flow which also improved projectcommunications

But ----- the price paid was a) speed and b) innovation.


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Software Development is NOTManufacturing (or is it?)

Software Development is extremely laborintensive

People are not uniform like machines used in

manufacturing.

Software Development often requiresinnovation

Every software seems to be a one of its kindalthough more and more are becomingstandardized

The same set of people do not get to repeatedlydevelop the exactly same software multiple times.Ch. 1 A Perspective on Testing -

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Improve Documentation (Availability andPresentation Technique)

Improve the creation and maintenance of documentsvia an on-linerepository or configuration manager

Centrally protected data Sharable data

Managed data (data relationships are managed)

Improve the usability and productivity byproviding more and better visualization of data

Replace numbers with graphs and figures Replace words with pictures

track, project, control


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Improve Testers Tools and Methodology

Test Methodology Improvements Test coverage analysis

Test case generation

Test-Fix-Integrate Process

Test results analysis

Test metrics definition and measurements process Etc.

Test tools improvements Test coverage computation

Test trace

Test script generator Test result records keeping and automated analysis

Build and integration (daily builds)

Etc.


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Perspective on Testing

Today we test because we know that systemshave problems - - - we are fallible.

1. To find problems and find the parts that do notwork

2. To understand and show the parts that do work

3. To assess the quality of the over-all product (Amajor QA and release management responsibility)


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Some Talking Definitions(IEEE terminology based)

Error

A mistake made by a human The mistake may be in the requirements, design, code, fix,

integration, or install

Fault

Is a defect or defects in the artifact that resulted from an error

There may be defects caused by errors made that may or maynot be detectable (e.g. error of omission)

Failure

Is the manifestation of faultswhen the software is executed.

Running code

May show up in several places

May be non-code related (e.g. reference manual)

Incident

Is the detectable symptom of failures

(Not in the text)

(includes error of omission and no-code?)

Note

Example? (bank accnt)


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Testing in the Large

Testing is concerned with all, but may not beable to detect allErrorsFaultsFailures

Incidents Testing utilize the notion of test cases to

perform the activities of test(s) Inspection of non-executablesExecuting the codeAnalyzing and formally proving the non-

executables and the executable in a businessworkflow (or user) setting


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Software Activities and Error Injections, FaultPassing, and Fault Removal

Requirements

Design

Code

Testing

Error

Error

Error

Fixing

Error

faults

faults

Faults/failures

Inspection

Inspection

Fixing

Note that in fixing failures, one can commit errors and introduce faultsCh. 1 A Perspective on Testing -

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Recording each Test Case

Test Case number

Test Case author

A general description of the test purpose

Pre-condition

Test inputs

Expected outputs (if any)

Post-condition

Test Case history:

Test execution date

Test execution person

Test execution result (s)


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Specification vs Implementation

Specification Implementation

Expected Actual

The ideal place where expectation and actual matchesThe other areas are of concern ---- especially to testers


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Specification vs Implementation vs Test Cases

Area S = Yellow=SpecificationArea P = Blue=Programmed-Implementation

Area T = Pink=Test CasesWhat do thesenumbered regionsmean to you?

S=Spec->Expected P=Program->Actual

T=Tested

56

2

4

1

3

7

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Black Box vs White Box code testing

Black box testing (Functional Testing)Look at mainly the input and outputs

Mainly uses the specification as the source fordesigning test cases.

The internal of the implementation is not includedin the test case design.

Hard to detect missing specification

White box testing (Structural Testing)Look at the internals of the implementation

Design test cases based on the design and codeimplementation

Hard to detect extraneous implementation thatwas never specified


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Recording Test Results

Use the same form describing the test case --- seeearlier slide on recording test case and expand theresults to include:

State Pass or Fail on the Execution Result line

If failed:

1. Show output or some other indicator to demonstrate the faultor failure

2. Assess and record the severity of the fault or failure found


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Failure Classification (Tsui)

Very High severity brings the systemsdown or a function is non-operational andthere is no work around

High severity a function is not operationalbut there is a manual work around

Medium severity a function is partiallyoperational but the work can be completed

with some work around Low severity minor inconveniences but the

work can be completed


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Fault Classification (Beizer)

Mild misspelled word

Moderate - misleading or redundant info

Annoying truncated names; billing for $0.00

Disturbing some transactions not processed

Serious - lose a transaction Very serious - incorrect transaction execution

Extreme Frequent very serious errors

Intolerable - database corruption

Catastrophic System shutdown

Infectious - Shutdown that spreads to others


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Increasingseverity


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IEEE list of anomalies (faults)

Input/output faults

Logic faults

Computation faults

Interface faults

Data faults

Why do you care about these types of faults (results of errors made)?

Because they give us some ideas of what to look for indesigning future test cases --- in process of for otherproducts developed by same people


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Different Levels of Testing

Program unit A

Program unit B

Program unit T

.

.

.

Function 1

Function 2

Function 8

.

.

Component 1

WholeSystem

Component 3

.

Unit Testing Functional Testing Component TestingSystemTesting


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Still Need to Demonstrate Value of Testing Catastrophic problems (e.g. life or business ending ones)

do not need any measurements---but--- others do:

Measure the cost of problems found by customers Cost of problem reporting/recording

Cost of problem re-creation

Cost of problem fix and retest

Cost of solution packaging and distribution

Cost of managing the customer problem-to-resolution steps

Measure the cost of discovering the problems and fixing them priorto release

Cost of planning reviews and testing

Cost of executing reviews and testing

Cost of fixing the problems found and retest

Cost of inserting fixes and updates

Cost of managing problem-to-resolution steps

Compare the above two costs AND include loss ofcustomer good-will


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Goals of Testing?

Test as much as time allows us

Execute as many test cases as (schedule) time allows?

Validate all the key areas

Test only the designated keyrequirements?

Find as much problems as possible

Test all the likely error prone areas and maximize testproblems found?

Validate the requirements

Test all the requirements?

To reach a quality target

State your goal(s) for testing. - - - what would you like people to

say about your system ? Your goals may dictate your testing process

Very important tothink about this ---

Quality Target?


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Documents

Ch1_A Perspective on Testing