SOURCE: Intertech

March 29, 2007 10:40 ET

Medical Device Unit-Level Testing Pinpoints Problems Early, Saves Time and Money, Intertech's Bernazzani Writes

NORWOOD, MA -- (MARKET WIRE) -- March 29, 2007 -- Unit-level testing of medical-device software adds initial work but ultimately saves time and boosts safety, David S. Bernazzani, a principal software engineer with Intertech Engineering Associates, writes in the current issue of Today's Medical Developments.

"The result is software that does what it is supposed to do and is far less likely to fail, to require costly rework, or to result in harm to patients," he writes.

Unlike black box testing, unit-level testing is based on detailed knowledge of the architectural and logical design, data structures, performance and timing specifications, and interface requirements.

Unit testing is a done at or near the code level to ensure that the implementation matches the intended design. Small sections of code, typically functions, are tested to ensure they work as intended and are reasonably robust. "It follows that larger groups of those building blocks will hold up better during integration," he points out.

Unit testing generally should be done at the smallest code level practical. Don't test at too high a level, as you may lose some control if you try to test too many functions at once, Bernazzani advises.

Unit tests should be written to verify that the code is a thorough and accurate implementation of the design described in the design documentation. The unit-test strategy should be planned as part of the design phase of development.

Creating code that contains a framework for unit testing is easier than trying to shoehorn unit testing in later. Finding errors during unit testing is also more cost-effective rather than waiting for problems to be found in systems tests, which take longer to develop, debug, run and process, he adds.

"The FDA wants independent review and testing of the device software as much as possible... Proper unit testing done early will make the code far more reliable as the software enters the remaining phases of testing. A little more time up front will pay dividends down the road," he concludes.

The full article can be read at

Intertech Engineering Associates, Inc. ( in Norwood, Mass., provides hardware and software development, requirements and quality engineering, product validation services, training and consulting for medical device manufacturers.

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