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Examples and Objects

The most successful and fun project I have been part of developed a network simulator for operator training. We had a great team and freedom to work how we wanted, but another key to success was the domain model. The analyst drew object diagrams to explain to the programmers and testers how a network topology could be, for instance like this:

This may look simple, but these diagrams explained a lot to us. We used them to discuss what should happen in different scenarios, such as what should happen when a Trunk is connected to another Port. Then we implemented these scenarios as unit tests. This resulted in a robust implementation with few bugs.

But in most projects, we don't have anything like this. In one project I spent several days trying to understand how a trading system worked. I had the domain model and database schema, but it was not clear when these objects were created, updated and deleted in the database. I read thousands of lines of code and run the program in a debu…
Recent posts

Writing Better Requirements with Examples and Screen Sketches

We were agile, we had a Scrum master, we had standup-meetings, we had unit tests, we worked iteratively and met the product owner regularly. We did everything right, except the requirements. When we were almost ready to launch, we suddenly understood that we had missed a critical piece of functionality; namely the complex pricing model. The product owner thought we knew how this should work, but we didn't. This was not a feature that could just be patched onto the application in the end, it took several weeks of restructuring. We might blame the product owner for not communicating this clearly, but we were the software professionals. It's our responsibility to find out what our customers want.

Examples What could we have done to avoid this embarrassment? Should we have spent the first month of the project writing requirements? No, I don't think that's the solution. That might have helped, but it would have cost too much.

There is a much simpler thing we could have do…

The Future of Programming

The problem with abstractions Programmers are experts in abstract thinking. To program is to generalize: A method is a general specification of different execution paths. A class is a general specification of objects. A superclass is a generalization of several classes.

Although our minds are capable of abstract thinking, concrete thinking is more natural, and concrete examples are the foundation for abstractions. For instance, how do you teach children what a car is? You don't give a definition like: 'A car is a wheeled motor vehicle used for transporting passengers.' Instead, you point at a car and say: 'Look, a car!' After seeing a few cars, the child understands what a car is.

Notice what I just did! I started with a general principle and then gave an example. Which part of the paragraph above is easier to understand, the first sentence (general) or the rest (example)?

Einstein said that examples is not another way to teach, it is the only way to teach. It is…

Back to the agile values

In recent years the term agile has become overused. Many seem to think that if they have have unit tests, standup meetings and burn-down charts, they're agile. All these practices are good, but they don't necessarily make you agile. Even iterations or some kind of certified master don't necessarily make you agile.

So what is agile? If I were to sum it up with one word it would be communication. Communication is everywhere in the agile manifesto:

[We value] individuals and interactions over processes and tools.
I see this as a reaction against processes like RUP that felt like a software development factory where developers were replacable cog wheels. Agile recognizes that it's individuals with intelligence, creativity and drive that make a project succeed.

But individuals are not working in isolation, they need to interact with others. Interactions means communication. Not one-way communication but interactive dialogues. Misunderstandings are inevitable in communication…

The problem with use cases

The greatest benefit I get from use cases is that they focus on the user. Use cases help me to think about what the user wants to do instead of only focusing on implementation details.

The biggest problem I have with use cases is that they are not structured. They are basically free text. For instance, if we have a use case Withdraw money from ATM, we may define that it has a precondition that Open account is performed, but we don't get any help from the method to see that.

What happens if someone later changes the Open account use case or defines a Close account use case? How do we find which other uses cases that need to be modified? We can look through the old use case diagrams and find dependencies, but I can almost guarrantee that these dependencies have not been maintained after they were initially created.

The solution to this is to connect the use cases to an object model. I don't mean a use-case realization with view and controller objects like ATM_Screen and ATM_Sess…

Getting the requirements right with object cases

One of the biggest problems in software projects is poor requirements. We always seem to misunderstand what the user is really trying to do or discover some missing functionality at the end of the project. Agile methods reduce this problem with short feedback cycles to discover misunderstandings early, but it would be even better to get rid of the misunderstandings before implementation.

Two things that really help me in this area are examples and objects. This article describes how to combine these with a method I am calling object cases.

An object case is an example of a user function connected to domain objects. It consists of 4 parts:
Initial objectsInputOutputResult objects
A typical week using object cases can be as follows:
Monday morning: Go through new functionality with the client.Monday afternoon: Planning and estimation.Tuesday: Implement automatic tests.Wednesday - Friday: Implement the actual functionality. My experience is that object cases help us a lot in all this activ…

Make it or break it

Some times I am working on a project alone doing both design, planning, programming and testing. I have found it useful to separate these different kinds of work as much as possible. That's because programmers are not good testers. Programming and testing requires totally opposite mindsets:
Success as a programmer is to get something to work (make it)Success as a tester is to find something that doesn't work (break it)If I start testing while I'm in programming mode, I will not try very hard to break it, so lots of errors will slip through.

But on the other hand, I can easily get into programming from testing. When I am testing, I am working with an example, and the example helps me to focus my programming. But I try to avoid jumping from programming to testing anyway, because it is hard to get back to effective testing again.

1. Design
I get the best results if I start with designing a few examples of how the functionality will be used. The examples help me to focus and remem…