My Musketeers for DotNet Test driven development

Test, four letters, one meaning and for some people a struggle. Getting people around you to write tests is easy only when everyone already agrees with you. As often, there are instances where some people show resistance to writing tests. Here is the stuff I hear the most from them:

D: I don’t have time to write tests.

A: I don’t need to test this.

B: I can’t write a test for this.

Not writing tests will always lead to hours of tears and blood. Tears and blood from debugging something you let slip through. Something that broke your super edgy software. I am not saying that writing tests will lead you to a bug free software but at least you know exactly how your code behaves. There, you know what you can reasonably expect from it. Despite having a great code coverage your code will eventually break and it’s perfectly fine. This is where your tests become useful as they will help you ensure you don’t break your existing code while refactoring or fixing a bug. Then you can simply add a new test to cover that unexpected scenario.

Per example, yesterday a colleague had some weird data mix up on a development deployment of an API I created a few months ago which revealed a case I didn’t think of. That API had 95% coverage and still a bug showed up because it is how software works. Although the bug was generated from a virtually impossible case, so what I did was replicate it, write a test for it, fix it and get it through review and released it all within 30 minutes. That project coverage is now at 98% (highest we have now, of course I’m gonna show off about it) and yet I know that one day or the other another bug will pop. When that day comes, it may not be fixed as quickly as yesterday but it will be as easy to refactor parts of it safely.

Yes it takes some time to write tests but on the long run it is more than worth it. For a long time I thought that the only reason for one not to cover his code would be laziness. Not the good laziness that makes you want to save time by writing tests and not spend hours debugging and testing a whole bunch of non covered features. Still, over time I came to learn that no developer walks to his desk everyday to write buggy code on purpose. A lot of factors come into play such as clients and project managers pressuring you with tight deadlines. Tighter and tighter deadlines, day after day. Then ensues a drop of quality in favour of faster delivery that in the long run can hurt a business.

In that kind of situation, blaming a developer for not writing tests will not help anyone. However, what can help is providing tools to help that developer to move faster. This is where today’s post is supposed to help you. Help you to accelerate your development. Today, I am using this post to present three tools that help me everyday to deliver code faster without sacrificing quality. Although nothing is magic, I hope these will help you in a personal or professional context as they help me every single day.

It doesn’t matter whether you have access to continuous integration or not. However, what will matter is your ability to write decent tests. Even if you write only very simple happy path tests, as long as you write those properly you will be fine. Here we go!

Moq

Moq is awesome for unit testing. What is unit testing? Well, I don’t have a proper definition in mind and there are tons of different versions online. The version I learned mostly over experience and you are free not to believe the same thing. To me, a unit test is a piece of software written to test a component regardless of the dependencies it has to make sure that a defined input will provide an expected output. Basically, unit tests allow you to validate your software’s behaviour in a way that prevents you or a potential collaborator from breaking it your software later on.

How does Moq works? The premise is that you can mock any interface which allows you to define how your software behaves based on a dependency input. Which is great in an inversion of control context. This also extends to class virtual and abstract methods so that you can create tests defining how a class behaves based on what a method could return. Another cool feature of Moq is the possibility to verify the methods of a mocked interface/class got called with a specific input. That will allow you to make sure that the method under test is calling its dependencies methods with the parameters you expect.

For more information on Moq you can check out their documentation on Github

AutoFixture

Let’s now move onto AutoFixture that I use pretty much since it exists. AutoFixture is a library that allows generating dummy data on the fly in any context. This thing made my test writing so much faster. It also works great with Moq to quickly write test cases where the input data does not really matter. You can use it to generate data of type, from string to bool to your custom classes. One of my main use for that library is to create data on the fly without thinking too much about it and use that generated data to validate my tests.

I have not reached the limitations of what you can do with that tool yet. However, you need to be careful with types that have a recursive relationship which you often get when you work using EntityFramework. Per example, if you have a Chicken class with an property of type Egg. Imagine that Egg class has a property of type Chicken, you will end up with an exception due to some kind of infinite loop situation. You can avoid that situation by defining what properties you don’t want to set when generating your data.

For more details on AutoFixture, check out their Github.  To jump straight to code samples here is their cheat sheet.

Postman

This one is a bit more different than the others mentioned previously. Indeed, you can use Postman to document how your API works. You can use it for monitoring with a paid account or build a monitoring of your own using Newman. I wrote a couple of posts about it over the past months to get started or to build simple CI using Appveyor. What I like with Postman is that it is pretty intuitive and straightforward to use even for non-technical people. Once you get started you can  do some pretty advanced flow-based testing which is pretty useful in micro services architecture. In the end, how and where you use Postman is down to you and I love the flexibility of it. That flexibility that allows you to make it fit your needs and accelerate your development.

Thanks for reading, you can now go and write a bunch of cool software with loads of tests. Or don’t. I’m not your dad and I won’t punish you, but your code will.

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