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16) Unit Test Mocks with Separation of Concerns

Coding With The Force edited this page Apr 18, 2021 · 11 revisions

Unit Test Mocks with Separation of Concerns

How does Unit Testing fit into Separation of Concerns?

The answer to this is simple, with Separation of Concerns, there is no unit testing, it just simply isn't possible. To unit test you need to be able to create stub (mock) classes to send into your class you are testing via dependency injection (or through the use of a factory, more on this in the next section). If all of your concerns are in one class (DML transactions, SOQL queries, service method, domain methods, etc) you cannot fake anything. Let's take a look at a couple examples to illustrate this problem:

Testing a class with SoC Implemented


Above you can see we are passing in fake/mock classes to the class we are testing and staging fake return results for the class methods we are calling. Thanks to separating out our concerns this is possible. Let's take a look at how impossible this is without SoC in place.

Testing a class without SoC Implemented


You can see above we did no mocking... it wasn't possible, we had no way of passing in fake/mock classes to this class at all.


How do I transition my Existing Code to start leveraging SoC so I can use Unit Test Mocking?

It's not a simple path unfortunately, there is a lot of work ahead of you to start this transition, but it is possible. The key is to start small, if you are a tech lead the first thing you need to do is find the time to train your devs on what SoC and mocking is and why you would use it. It's critical they understand the concepts before trying to roll something like this out. You cannot do everything as a lead even if you'd like to, you need to build your team's skillset first. If you aren't a lead, you first need to convince your lead why it's critical you start taking steps in that direction and work to get them onboard with it. If they ignore you, you need a new lead... After accomplishing either the above you should do the following:

  1. Frame your situation in a way that the business arm of your operation understands the importance of altering your code architecture to leverage SoC and unit testing. This is typically pretty easy, just inform them that by spending a few extra points per story to transition the code you are going to gain more robust testing (resulting in less manual tests) and that the code will become more flexible over time, allowing for easier feature additions to your org. Boom, done, product owner buy in has been solidified. Ok, lol, sometimes it's not quite this easy, but you know your business people, give them something they won't ignore, just be careful to not make yourself or your team sound incompetent, don't overcommit and make promises you can't keep and frame it in words business people understand (mostly dollar signs).

  2. Start small, take this on a story by story basis. Say you have a new story to update some UI in your org, with business owner buy-in, tack on a few extra points to the story to switch it to start using SoC and Unit Testing. Then, MAKE SURE YOUR TESTS ARE INCREDIBLE AND YOU TRUST THEM! I say this because, if your tests are incredible you never have to ask for permission again... I mean think about it, wtf does the average business person know about code. As long as I don't introduce any new bugs I could change half the code base and they'd never even know. If your tests are golden, your ability to change on a whim is as well. Make those test classes more trustworthy than your dog (or cat I guess... but I wouldn't trust a cat).

  3. Over time, your transition will be done... it might take a year, it might take 5 years, depends on how busted your codebase was to begin with. Hopefully, by the time you are done, you have an extremely extensible codebase with tests you can trust and you never have to ask for permission to do a damn thing again.


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Part 17: Implementing Mock Unit Testing with Apex Mocks

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