Coded UI testing: What is the reasoning behind creating multiple individual UIMap classes instead of just multiple partial UIMap classes?

Question

I am working on a project which includes a "semi-big" application GUI. There are about 4-5 individual(complex) pages I want to perform Coded UI Tests on, and I have gotten the impression that creating multiple UIMaps is the way to go! Sources: UIMap container, Using multiple UIMaps, More source and the list could go on...

My problem/thought: Using multiple UIMaps is "nice" because it:

1. allows a more categorized structure of the code
2. allows easier cooperation between developers
3. makes the code less daunting to maintain.

But why is no one merely chopping the UIMap up in multiple partial classes? Wouldn't it still have the same advantages? Even further: Having the UIMap in partial classes will prevent the developer(me) from adding complexity to the code like UIMap container.

Answer 1

This question is not really specific to CodedUI. Using partial classes to simulate separation of concern is not the correct way to go.

They might make writing a class easier, but they do not create proper separation of concern (which is the underlying reason behind the existence of classes) and thus do not make using the class easier, since from an external point of view there is no difference at all between a class with code written in one or several files.

To give a simple example, you will have auto-completion return a flat list of all the members of your class accross all partial files without distinction.

Partials are used when a class is part generated code part non-generated code, or written in different languages (xaml and C# for SL/WPF for instance). The different bits might cover parts of the same behaviour, hence it makes sense (from an SoC point of view) to group them under the same class, but from a code management perspective, the two parts need to be separated. This is why CodedUI uses partials (*.Designer.cs files are generated, while *.cs files are not).

If you feel the need to create partials to have separation of concern, then you should probably take a step back and use proper SoC (i.e. create different classes).

In the specific case you are exposing, I would consider creating UIMaps for different sections of your application UI (whether your are separating the behaviour of your UI into different windows, or sections of windows, etc - depending of the complexity of it).