How To Be MEAN: Test Me MEANly

Ted Neward. MSDN Magazine. 2016-01-01
Ted NewardHowdy, “Nodeists.” Welcome back to the continuing saga of input, output, databases, users, UIs, APIs and parallel universes. (See the first part in this series [msdn.com/magazine/mt185576] if you missed that reference.)
In the previous installment (msdn.com/magazine/mt595757), the application had grown to the point where the API endpoint being built (a super-simplified “persons” database) rounded out its CRUD facilities to include the CUD, where the previous installment had provided just the “R.” Building out in small steps is important, certainly, but it’s nice to have something that can see changes to it and reflect them back when asked about them.
This brought up an uncomfortable point. When building a Web API such as this, “easy testing,” in which a developer can just fire up the Web page and eyeball it to determine whether something is working correctly, isn’t an option here. Well, sure, as pointed out last time, using tools such as cURL, Postman or Runscope can help make it easier to eyeball it, but frankly, trusting eyeballs isn’t really the point. The application needs some automated tests to help make sure everything is running smoothly and correctly. It should be a test suite that’s easy to run, covers the code well and has all the other characteristics that so many others have documented far better than I can.
One note before I go too deep down this path, though. There’s a bit of debate around “unit” tests, which have intricate knowledge of the inner workings of the code and (usually) require some level of mocking (in this case, the Express request and response objects, for example). These are supposed to be small, focused and execute quickly so they can be used as part of a build process (right after compilation, for compiled languages like C#) without slowing down programmers and jerking them out of the flow of their thoughts. Another view is that of “integration” or “feature” tests, which are more “external” tests, meaning the test relies on the frameworks to do their thing and treats the layer as a more opaque entity. For Web APIs, I tend to favor the latter; I’ve found that trying to write unit tests over Express controllers can often be more work than benefit to get all the mocking right. Given that controllers are generally intended to be single-purpose, anyway, and there are few, if any, bugs I’ve found in the Express layer that interferes with testing my own code, I’ve found external tests to be a better value in the bang-for-your-buck discussion.
With that out of the way, it’s time to write some tests that exercise the persons API I’ve built so far. And to that end, there are two Node.js packages that immediately come to mind: mocha and supertest.

[The Working Programmer – How To Be MEAN: Test Me MEANly]

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