Regression testing of medical devices
by itsbusiness AG
During development of medical devices, software standard IEC 62304 must be followed, and regression testing is a vital part of the Quality Assurance process.
Regression testing is the rerunning of test cases that a program has previously executed correctly and comparing the current result to the previous result to detect unintended effects of a software change. The FDA stated that 79% of all software errors are introduced during the modification of already released software, the best way to mitigate this is with regression testing. It is also important to detect any defects introduced by software changes early, as the cost to fix a defect later in a development cycle is much more expensive. Regression tests need to be maintained and added to when new functionality is added.
Wherever possible, regression tests should be automated and used within a Continuous Integration (CI) system. This will ensure that the tests are run against modified software as soon as possible and any defects introduced will be detected immediately. The aim should be to automate more than 70% of the tests.
Regression tests should cover all main functionality of the device. This is best done by integrating the device into hardware-in-the-loop (HIL) testing. HIL testing is when device software is downloaded onto the device in a physical testbed, and then tests are run automatically on the device. The aim is to verify that the device is functioning correctly.
Automated testing can also be done over a longer period, to detect reliability problems. For example, tests which check that the device runs correctly over an extended period (overnight/days). These will detect possible glitches in the underlying system, including race-conditions.
An example of automated reliability testing with HIL is testing a treatment cycle over four days for an insulin pump. The test sets up all the parameters for treatment and executes all the injections. The test checks that the treatment cycle has been executed correctly. Checks done include making sure that the injections are made with the requested volume at the correct time. Automation is a much better way to do this than manual testing.
Clear requirements are a pre-requisite for effective testing, test cases should be developed against requirements. An analysis of what options are available for communicating with the medical device needs to be done. Options include Bluetooth and UART connections. The device software should support commands/queries that the tests can access, as these will form the basis of the tests.
With more than twenty years’ experience in QA management and implementation, Itsbusiness AG can help with testing during the full lifecycle. We work with customers to clarify requirements, define test cases, and automate testing including setting up hardware-in-the-loop testing and Continuous Integration systems.
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