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QUEST Webinar:
Intelligent Defect Sampling
An Innovation for Focused
Testing
Featuring
Randy Rice
Rice Consulting Services
WEBINA SERIES
presents the
WEBINAR SERIES
www.qaiQUEST.org/2018
DEFECT SAMPLING – AN
INNOVATION FOR
FOCUSED TESTING
RANDALL W. RICE
RICE CONSULTING SERVICES
WWW.RICECONSULTING.COM
© 2014, Rice Consulting Services, Inc.
3
THE BIG IDEA
• As testers, our job is to find defects.
• However, we often look for only the
symptoms of defects – failures.
• All testing is sampling
• What if…
• We had ways to sample for defects?
• Defects really do cluster?
• We could predict where best to look for
defects?
• We looked for defects differently?
4
THE BAD NEWS
• As testers, we suffer from the “needle
in a haystack” problem.
• Looking for something very small in
something very large.
• However, a metal detector helps!
“WE NEED
PEOPLE TO
TEST WHO
DON’T THINK
LIKE TESTERS”
CEO TO TEST MANAGER
6
WHY?
• When “professional” testers miss obvious
things, business stakeholders rightly look for
other solutions.
• It’s common for:
• Our methods to get old and ineffective
• Testers to grow complacent
• People to fail to learn
• Our perspectives to get too narrow
• People to have misplaced priorities
7
POLL QUESTION #1
• Do you feel challenged by the problem of “Too much
testing, too little time and resources”?
8
A GOLD MINING
ANALOGY
• Gold mining is an expensive task, even on a small scale.
• Testing can also be expensive.
• There are often places that look promising for gold.
• But there is no way to tell from the surface if gold is really underground.
• The only way to know for sure is to drill holes and sample the dirt.
• In testing, we can do something similar as a way to test our intuition and suspicions about where defects may be.
• Test automation is a creative way to drill for defects.
9
NO HELPFUL SIGNS!
10
WHAT DO WE SEEK?
Failures
Externally Visible Through Functional (Black-box) Testing
Internally Visible Through Structural (White-
box) Testing and Static Analysis
Defects
11
THE PROBLEM
• External
• Too much to cover, too little time
• Unclear expected behavior
• Test automation mainly used for
confirmatory testing
• Internal
• Lack of technical knowledge by testers
• Lack of motivation from developers
• Lots of code!
• Many interactions
• However, there are some very helpful
static test tools
12
Defect
THE CONCEPT
Sample 1Sample 3
Sample 4 Sample 6
Defect
Visible Feature Sets
Above the surface we use a lot of
guesswork.
Below the surface is
where the defects are.
Sample 2
Failure
Sample 5
Failure
13
ADJUSTING THE
SAMPLES (TESTS)
Sample 7Sample 2
Sample 8
Sample 9Sample 5
Sample 10
Defect
Defect
DefectDefect
Visible Feature Sets
When we find a
defect, there may be
others nearby.
14
LOOKING BELOW THE
SURFACE
Sample 7Sample 2
Sample 8
Sample 9Sample 5
Sample 10
Defect
Defect
DefectDefect
Visible Feature Sets
Failure
Failure Failure
FailureFailure
15
PATTERNS TELL US
SOMETHING
Variation Consistency
Sights are
probably OK, but
we need to work
on accuracy
Sights are off, but
we are consistent
in our aim.
Other variables could have
an impact: Wind, distance,
etc.
16
THE KEY – LOOK FOR
PATTERNS
• Patterns help us find interesting defects.
• Commonality
• Concentration
• Contrast
• Types
• Trends
Pearson's correlation
18
HOW CAN WE
SAMPLE?
• Classes
• Risk
• Relationships
• Statistical Methods
• Randomly
19
CLASSES – SAMPLE 1
Input Types
Process
Types
Output Types
Defect Types
Input
Values
Output
Values
? States
Transient
Data Values
20
CLASSES – SAMPLE 2
Input Types
Process
Types
Output Types
Defect Types
Input
Values
Output
Values
? States
Transient
Data Values
21
RISK LEVELS –
SAMPLE 1
Very High
High
Moderate
Low
Likelihood
Impa
ct
High
Hig
h
Low
Low
22
RISK LEVELS –
SAMPLE 2
Very High
High
Moderate
Low
Likelihood
Impa
ct
High
Hig
h
Low
Low
23
RELATIONSHIPS
Is it possible to withdraw money from a closed
account with a positive balance?
24
STATISTICAL SAMPLING
• Population analysis
• Used to model test data based on production data.
20% 20%60%
0 – $1,000 $1,000 - $1,500 > $1,500
Value of annual customer orders
20% of
accounts < $1,000
20% of
accounts > $1,500
60% of accounts between
$1,000 and $1,500, inclusive
25
TEST DATA MODELING
20% 20%60%
0 – $1,000 $1,000 - $1,500 > $1,500
Value of annual customer orders
20% of
accounts < $1,000
20% of
accounts > $1,500
60% of accounts between
$1,000 and $1,500, inclusive
20% of test
accounts have
balances less than
$1,000.
60% of test accounts
have balances between
$1,000 and $1,500,
inclusive. 20% of test accounts
have balances greater
than $1,500.
26
RANDOM SAMPLING
• Not a substitute for other approaches
• However, it can be helpful at times to help get off the
beaten path.
• Examples:
• The first n rows of data
• Every nth occurrence
• Random number generators
27
POLL QUESTION #2
• Do you currently use test design techniques such as
equivalence classes and/or statistical sampling?
28
HOW CAN WE
LEVERAGE THIS?
• Test Automation
• Frameworks to vary inputs and actions:
• Randomly
• Based on defect patterns and clustering
29
EXAMPLE
• There are 10,000,000 possible values for a field variable to
be tested.
1. Extract or build test data based on the values to test and
the randomizing formula chosen.
2. Create automated tests using the data as input.
3. If a failure is seen, capture the test values and test a lower
to higher range.
30
EXAMPLE (2)
0 10,000,000
Failure
5,001,004
✔ ✔✔ ✔
5,001,0044,999,999 5,010,000
Failure
Range
31
THE MISSING LINK –
FEEDBACK FROM MISSED
DEFECTS
32
ENDING THE CYCLE
OF DEFECTS
• Defects = Rework = Lost $$
• The cycle continues until broken
Fix
Same types of defects
FindCreate
Same types of defects
33
THE FEEDBACK LOOP
Identify root causes and fix the process
Fix
New types of defects
FindCreate
New types of defects
34
USING DEFECT FEEDBACK
FOR TEST DESIGN
Identify root causes and fix the process
Find Fix
New types of defects
Create
New types of defects
New tests
35
POLL QUESTION #3
• Do you perform root cause analysis to prevent defects
based on the information from testing?
36
When you consider
the cost of a post-
release defect, the
value gained in
preventing defects
is like finding gold!
Failure Costs (Fix,
Rework)
Review & Test Costs
Prevention Costs
Cost of Production
Cost of Quality
Cost to Build
(Development, Delivery)
37
When you consider
the cost of a post-
release defect, the
value gained in
preventing defects
is like finding gold!
Failure Costs (Fix,
Rework)
Review & Test Costs
Prevention Costs
Cost of Production
Cost of Quality
Cost to Build
(Development, Delivery)
Found Value! Profit!!
38
SUMMARY
• Failures are only symptoms of defects.
• Not every defect manifests a failure.
• Not all failures are defects.
• Before spending valuable time designing
and performing non-productive tests,
intelligent test sampling is a good way to
focus your efforts.
• No drill, no dig!
39
BIO - RANDALL W. RICE
• Over 35 years experience in building and testing information systems in a variety of industries and technical environments
• ASTQB Certified Tester – Foundation level, Advanced level (Full)
• Director, American Software Testing Qualification Board (ASTQB)
• Chairperson, 1995 - 2000 QAI’s annual software testing conference
• Co-author with William E. Perry, Surviving the Top Ten Challenges of Software Testing andTesting Dirty Systems
• Principal Consultant and Trainer, Rice Consulting Services, Inc.
40
CONTACT INFORMATION
Randall W. Rice, CTAL
Rice Consulting Services, Inc.
P.O. Box 892003
Oklahoma City, OK 73170
Ph: 405-691-8075
Fax: 405-691-1441
Web site: www.riceconsulting.com
e-mail: [email protected]