Transcript Zodiac Systems - IEEE Twin Cities Section

Testing in the Design
Phase – Medical Devices
Ralph Cardinal
5/19/05
© 2005 Ralph Cardinal. Copying and distribution of this document is permitted
in any medium, provided this notice is preserved.
Some definitions…
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Design Analysis Testing (DAT)
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Evaluates correct implementation of the design intent, and
requires intimate knowledge of the design detail.
Performed by designers, or dedicated group of DAT testers.
Typically tightly coupled to designers. Verifies that
implementation is correct as intended and meets
requirements. In addition, allows designers to exercise design
in extreme ways. White box testing.
More definitions…
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Design Verification Testing (DVT)
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Demonstrates that specified requirements have been met.
Typically performed by independent group, sometimes called
QA, especially in SW word. Verifies design to requirements.
Black box testing.
Design validation
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Demonstrates that the system conforms to user needs and
intended uses.
Performed by independent group, or more likely, the
designers and system engineers.
Why Test?
Test Approaches
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Over the Wall Model
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Gated Model
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Design to a point, then test, reapeat till complete
Spiral Model
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Separate test and development groups
Design expects test to help “test in” quality
Design identifies features to be complete, performs test, then allows
verification testing to be performed on design. Defects are “spiraled”
back into design effort for next feature set release
V-Model
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Design and test develop design and tests in parallel, using common
requirements, meeting at the point of the ‘V’. Requires great
communication and excellent requirements.
What to test in Design?
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Hardware
Software
Systems
Hardware
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DAT
DVT
Integration
Systems
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Module
Integration
Verification
Validation
Regulatory Expectations
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Verification and Validation
Documentation
Meets expectations of customers
Safe
Reliable
User Interface / Human Factors
Good Practices
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Independent Verification and Validation (IV&V)
Peer Reviews and Inspection
Design Analysis Testing
Planned, methodical, and documented test
process and execution
Questions from previous meeting
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What does software need to create for the testers,
especially if testing is done before the software exists?
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Requirements, Requirements, Requirements
What does design phase testing mean?
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Early DVT testing and development
Design Analysis Testing (DAT), unit tests, early integration
testing
Specific feature set testing, phased testing
Questions from previous meeting
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How should software developers approach
testing?
DAT
 Unit test
 Integration testing
 Automated and/or scripted wherever possible
(regression tests)
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Questions from previous meeting
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Do they need to think in a specific process?
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Absolutely, should the following:
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Plan
Methodology
Protocols
Cases
Report
Do they need to create a test, eg. test driven
development?
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Covered in approach/strategy and plan agreed to by the team
Questions from previous meeting
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What does it mean to the integrity of the test
process if testers are part of the design process?
Commonly believed the IV&V (Independent
Verfication and Validation) is better
 Integrity is probably the wrong word
 Testers need to be testing, at a minumum, areas they
have not participated in the design to get a good
second view and fewer assumptions about how the
software, system, module should be functioning.
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Questions from previous meeting
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How do they remain separate and 'part of the
loyal opposition'?
Separate team is typically the best
 Smaller development teams, hardware engineers can
test software and vice versa if skilled appropriately.
(Common in embedded designs)
 Inspection in the design phase yields many more
dividends, early detection, and more defects.
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