Yet another Mock Object “framework” for VA Smalltalk


I’m currently preparing a training/workshop for a new customer where we want to find ways and techniques to improve their use of unit tests in a legacy Smalltalk project. They’ve been using VA Smalltalk for a couple of years successfully and provide a very respected family of products in their field. In fact, they say they are a market leader in the very business. After a few years of trying to ignore the fact they successfully use Smalltalk in their product, they’ve come back to a point where they accept it as a useful technology that has its place and benefits – even if it is not considered mainstream.

So they – like many other Smalltalk projects – are faced with the fact that they missed the train for unit tests and code improvements in their Smalltalk pool while most other teams adopted these techniques years ago. So now they need to find a way to get their product under test without breaking it. Not that this can’t be done, it’s just a question of where to start and how to get all team members into the same boat while accepting that there is no chance to get a significant percentage of test coverage any time soon.

But back to what I wanted to write about. I am going through notes and code snippets of projects I’ve worked on to find useful stuff that we can use as starting points or discussion base for their specific way to test land. I stumbled upon a little Mock Object implementation that I had implemented back when I was young, so much younger than today… (wait, isn’t that some line from an old Beatles song, that’s even older than that?).

It simply consists of one class that can be configured to answer messages with defined results and interview it how it went after it was used. The whole thing was inspired by an old blog post by Sean Malloy and is really a neat, tiny and feature-poor simplest thing that could possibly work. Nevertheless, I couldn’t find a ready-made Mock Object implementation for VAST on G, so I thought it probably won’t hurt if I uploaded mine.

So there it is on VASTGoodies, ready for you to explore, use, extend and post a better version back to VASTGoodies. Feel free to like it or port another one to VA ST, there are several better ones available for VisualWorks, Squeak and maybe more.

There really isn’t much to say about the tool, other than that it’s easy to setup and use, you can always take a loot at the TestCase in the MiniSMockTests Application that comes with MiniSMock.

Here’s a mini-tutorial for MiniSMock:

You set up a Mock Object like this:

mock := MockObject new.
mock answer: #test with: [Date today].
mock answer: #sayHelloTo: 
  with: [:aPerson| Transcript show: 'Hello, ', aPerson asString;
    cr. aPerson].
mock answer: #sayHelloTo:and:
with: [:aPerson1 :aPerson2| Transcript show: 'Hello, ',
   aPerson1 asString, ' and ', aPerson2 asString; cr. aPerson2].

and you can then send messages to it. Just like this:

mock sayHelloTo: 'Joachim'.

In a Testcase you can then ask a MockObjects a few questions:

mock receivedMessage: #sayHelloTo:.
mock receivedMessage: #sayHelloTo: withArguments: #('Joachim').

And that’s all folks.
But don’t underestimate the power of Mock Objects when it comes to introducing unit tests in a legacy project!