Model based testing - the future?

So there is this thing: model based testing... sometimes they call it property based testing. The concept is simple, instead of writing test cases (which can be really, really inefficient) you just tell to a droid what to do. Of course it is not that simple... the droids nowadays requires a lot of explanations...

In nutshell it means the following: you create a finite state machine which is the expected behavior of you application, and based on that, you can generate tests.
The edge describe the action what you need to do with the system under test, and the node is the expected state, so the content of your assertion. Sounds simple...

My previous experiences with model based testing were...

• If there is any tool support for visualizing and executing, storing, creating, whatever, it is really expensive, and it tells you the way how you can interact with the system....  you are strongly binded to the tool.
• After a while, when you try to cover all your requirements with the model you end up with creating a huge, unmaintainable monster, what is more difficult to understand than the implemented system, and the hair stand up on the back of your neck if you just think that you have to change it
• so you decide to throw it away and implement tests based on your requirements and your inspiration, with a few comments, so everyone can understand what is the feature/method about...

But what do we have now?

In the last few months I started to use two tools... well I am not extremely experienced in any of them, but at least I am familiar with the features it can give to a QA engineer. Both tools are similar in a few points:

• you use a programming language to implement your model based test
• so you have to do your own FSM implementation
• the tool provides you the bricks what you can use to build up your model:
• a transaction/action where you call a method to change the state of the system under test (aka test call)
• a post condition where you can check is the state of your application is what you expect (after the log in I have a proper session)
• a precondition/guard where you can filter those transactions out what you do not want to call with the given state (logout when you are not logged in)
• next state: where you can change your state (it only exists in one tool, in the other you have to put it in the transaction or in the post condition)
• and the tool gives you other features to make the execution better (on this level, they are really different)

So the bricks are simple. A lot depends on you, and how you implement this thing. And here the KISS principle is critical.

And there is another thing about model based testing. As a tester we want to think on end-to-end level. We use the requirements to create tests, we try to put ourselves in the user's/customer's mind, we want to discover those cases when something can go wrong. And it is hard to align these things with model based testing...

Why?

Sometimes it is just too much for a model, you must keep it simple!

So I can imagine two strategies to create the model:

1. Find that area in you application which is the most critical, but relatively small. And apply an extensive model for that (so you have to reduce your scope, to not have a large model).
1. Benefit? your model won't be complex, and your critical part will be covered. And do not forget, you can have multiple models for different aspects/parts...
2. Step back, and view the whole system, and collect those interactions what your users will normally do with it, and create a model based on that. So basically you connect the happy paths together, to see if with a long, diverse usage, your application is still flawless. 
1. Benefit? your model is not complex, because your functional tests will focus on the edge cases, and other parts of the requirements, what is to expensive to cover here.

So that's it for today, in the next posts I will introduce the tools for you, and what I tried (and failed), and finally done (and doing) with it.