Saturday, 14 July 2018

Mocking

Some projects seem to encourage the use of mocks, why not? they're really powerful right!! "I can do all kinds of stuff with them!" Personally I find mocks to be at the extreme end of the scale, while they are a really powerful and useful tool, I rarely need them. And why add complexity when it's not required. Even the best setup interfaces are pretty complex.

Most of the time you can get around mocks by restructuring your code to have the execution of the dependencies fired outside of the place the testable logic occurs. The easiest illustration of this is database calls, Load the data and Save the data externally to any manipulation or calculation logic you are doing on this. This means the construct that accepts the data and returns some other data can be tested by passing variables and checking what is returned.

Perhaps the logic needs to call another service to let it know when something happens, realistically I can't say that not using mocks will work in every case. But you should defiantly ask yourself if you can move the calling code into another place that isn't as testable. Perhaps the service could return the message to send to the other service. Do we really get a lot of value out of testing that we passed what we guess is the right thing to the network abstraction. Would this not be better to test in an integration test where we test a call to the real service.

Sometimes the things get to a point when we need to use mocks, but I think people don't often spend enough time trying to avoid them and make simple input output tests.

Another example could be I have a method that add's data to a database, and a method that gets data from a database. I mean I could mock the DB and interaction test that the right looking things were passed. But I'm really testing thats it's implemented how I implemented it. To me personally checking that the code I wrote works in the way I wrote it adds no where near as much value as testing that it does what it's supposed to do, no matter how it does it. In this example we could easily call the add method, then the get method and check that the correct information is returned. We can set the database to in memory mode, or use a memory based abstraction round the database. If your testing is really stringent then you should probably at least have an integration test on top of this that checks the database functionality works as expected as well.


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