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Discussion on: Unit Testing - is it necessary

cgeorgian profile image

Are they really? I can se how this might apply to the early stages of a project with enough discipline and experience also thrown into the mix. But what about legacy/existing code. Sprinkling some small changes into a method wo UTs would result in a couple of hours of mocking, stubbing and dummy-ing.

stretch0 profile image
Andrew McCallum

I would agree that retroactively trying to add unit tests to code that you're not familiar with / didn't write can be a little more tricky but not impossible. This isn't unique to unit tests though as the same applies to integration and E2E.

In saying that, if you're working with legacy code, I think it is fair to assume that you're still adding code / features / bug fixes. It is at this time when you can add those tests (unit or otherwise) as you have more familiarity with the code. This would be akin to following the boy scout rule.

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zakwillis profile image
zakwillis Author

I am coming from it more that if we write applications which are data focused - integration tests are better. A great example could be coding in a portfolio swap for a known test case, if this is stubbed that stub can become stale quickly. In this example, I may store the stub as a json file (deserialised IList). This allows testers and analysts to put in their own test cases. I wrote about this here (kind of)

I think your point is valid, imagine if there is legacy code. Yes, I would probably setup up a separate unit test project as a means of understanding the code. However, where legacy systems exist, they are only understood by their outputs - which again leans towards integration testing, despite how slow the process may be compared to unit testing.