matt archer - how to regression test a billion rows of financial data every sprint - eurostar 2012
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www.eurostarconferences.com
Matt Archer, Independent Software Tester, UK
How to regression test a billion rows of
financial data every sprint
@esconfs #esconfs
Big data (a pension scheme example)
2
x x = 100,000 people
12 months
100 years
1.2 million estimates
1.2 million estimates
10s of financial models
x A Very Large
Database! = Billions of
database rows
Creating a website
3
Page 1
Page 2
Page 3
Pages to develop + test
Sprint 1
Creating a website
4
Page 1
Page 2
Page 3
Page 4 Page 6 Page 5
Pages to regression test
Pages to develop + test
Sprint 1 Sprint 2
Creating a website
5
Page 1
Page 2
Page 3
Page 4 Page 6 Page 5
Pages to regression test
Pages to develop + test
Page 8 Page 7 Page 9
Sprint 1 Sprint 2 Sprint 3
Page 11 Page 10 Page 12
Creating a website
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Page 1
Page 2
Page 3
Page 4 Page 6 Page 5
Pages to regression test
Pages to develop + test
Page 8 Page 7 Page 9
Sprint 1 Sprint 2 Sprint 3 Sprint 4
Page 11 Page 10 Page 12
Creating a website
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Page 1
Page 2
Page 3
Page 4 Page 6 Page 5
Pages to enhance + test + regression test
Page 8 Page 7 Page 9
Pages to regression test
Pages to regression test
Sprint 1 Sprint 2 Sprint 3 Sprint 4 Sprint 5
A common approach
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Regression Test Strategy 1 (“The Regression Pack”)
1. Re-run tests from previous sprints.
2. Select those tests using a risk-based heuristic (rule of thumb).
3. Automate as much as possible, increasing the coverage over time.
An example web page with financial data
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Example of a data-checking test
Given… …an organisation with approved data
When… … a user selects an Information Type of “Present Value” a Timeframe of “Weekly” and a Grouping of “Individual”
Then… … the data should be aggregated accordingly*
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132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987
132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987
132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987
132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987
132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987
132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987
132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987
132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987 132473943987
* Much better BDD examples exist. Opted for brevity over clarity.
2 x 3 x 3 = 18 Data permutations
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18
How many permutations for an entire site!?
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Page 1
Page 2
Page 3
Page 4 Page 6 Page 5
Pages to enhance + test + regression test
Page 8 Page 7 Page 9
Page 11 Page 10 Page 12
Pages to regression test
Pages to regression test
The thoroughness vs. maintenance conundrum
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…create those tests if you
Think they’ll find bugs!
Follow Your
Instincts…
BUT more tests = more maintenance
An alternative approach
So, what is the alternative?
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An alternative approach
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Regression Test Strategy 2 (“Capture and Compare”)
1. Take snapshots of the data as it is
displayed in a known high-quality build
2. Store the snapshots somewhere safe
3. Use the snapshot to help identify unforeseen changes (bugs) in future release candidates and live releases
Step 1: Identify a gold build
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Page 4 Page 6 Page 5
Page 8 Page 7 Page 9
Page 11
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Page 1
Page 2
Page 3
The “Gold” Build (1.3.2.14)
I’m so great, I’ve been the subject of…
BDD Unit Tests
Integration Tests Exploratory Testing
UX Inspections SME Reviews
Customer Demos
And maybe even… production use
(with NO complaints!)
Step 2: Specify the data permutations to capture
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<WebPage path = “/analytics”>
<QueryStringParam name = “InformationType”>
<QueryStringValue value = “PresentValue”/>
<QueryStringValue value = “Cashflow”/>
</QueryStringParam>
…
…
</WebPage>
Step 3: Capture and clean the HTML tables
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Capture specifications
Capture
String Host String Spec_Location String Save_Location
Void Capture() Void Clean()
Data snapshots
<table> <tr> <td>4.24</td> <td>15.93</td> <td>12.67</td> … </tr> … </table>
Selenium
“Gold” build
Step 4: Synchronise the data
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Database
Database Synchronise
Release Candidate “Gold” Build
Step 5: Compare the release against the snapshot
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Compare
String Host String Spec_Location String Snap_Location
Void Compare() Void Highlight()
Data snapshots
Capture specifications
Highlighted release candidate
Release candidate
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Step 6: Manual validation
What is a bug? What is a deliberate change?
What to capture, what to test?
What to capture? What to test?
The final build from the previous sprint
The final build from the current sprint
The build currently deployed in live
The build currently deployed in staging
The build deployed in live prior to release
The build deployed in live after the release
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• The technique can support a variety of team milestones
Summary
• Beware generic regression testing (or any testing) strategies
• Look for more efficient ways of detecting regression bugs
• Balance your regression techniques
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Questions?
Matt Archer
August 2012
Twitter: @MattArcherUK
Blog: mattarcherblog.wordpress.com
Email: matthewjarcher@googlemail.com
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