Wednesday, February 7, 2018

Integration Testing, part 6: Updating requirement based on integration testing


So now we have 2 types of integration tests giving us information on our muffler + engine system.  We are checking both the documentation (data sheets) of each component to ensure they will work together.  We also test the physical system itself to validate the real world behavior.  This way we can ensure the car will actually work after we build it.

There is one last aspect of this I want to cover.  There is a possibility that we actually decide to change engines or mufflers at the midpoint of the design process.  One reason for this could be the result of our testing.  If we notice that, at maximum engine RPM the muffler is at 100% capacity we may decide we need a larger muffler if the engine has a possibility of over-revving.

In this case, we need to back up a few steps and update our documentation.  If we move from Muffler Model 100 to Model 200, we need to update our specifications that we use in our computer automated test.  We have to take into account the different capacity of the new muffler - we clearly want to ensure the model of muffler we are committed to using has valid statistics.

We also will need to update our physical test as well, and this may be a little easier to understand.  If the muffler has a different size, we may need to move our sensors, the mounting bracket for the sensors, and so on.  We may need to change our tolerance levels as well.   If we had set a warning that the engine was exceeding the capacity of the old muffler, we will need to change that setting to reflect the capacity of the new muffler, for instance.

At this point we now have updated specifications, updated tests and can quickly validate how well the muffler + engine work together.  Had we missed either step in updating the changing requirements, we run the serious risk of not being able to tell that the engine + muffler would not work. 

I'll cover the costs of finding these errors when I sum up next week.

Questions, comments, concerns and criticisms always welcome,
John


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