assert-extensions

Extensions for VisualStudio UnitTest's Assert class to simplify e.g. testing of view models.

What is this

This project provides "timed-out" assertions as C# extension methods for Visual Studio UnitTesting Assert class. The extension methods can be useful when testing e.g. async void methods. See examples for more.

In the future, there could be more extension capabilities for testing. Leave your suggestions in the issue tracker.

Problem

Consider for example a RelayCommand inside a view model that has a string property MyTextProperty. It takes an Action as a parameter (here, as an async lambda expression):

RelayCommand MyCommand = new RelayCommand(async () => 
{
    bool ok = await DoSomethingAsync(); // DoSomethingAsync returns Task<bool>
    MyTextProperty = ok ? "finished" : "failed";
});

How to test it? Maybe like this?

viewModel.MyCommand.Execute(null);
Assert.AreEqual("finished", viewModel.MyTextProperty);

...but executing the command will just fire and forget.

So maybe adding a delay helps:

viewModel.MyCommand.Execute(null);
Task.Delay.Wait(1000);
Assert.AreEqual("finished", viewModel.MyTextProperty);

...but what should the delay be?

Example

If you don't want to refactor your view model code completely just to test it, you can use these extensions:

viewModel.MyCommand.Execute(null);
Assert.That.PropertyEquals("finished", () => viewModel.MyTextProperty);

This will poll for the value and return until viewModel.MyTextProperty equals "finished", or it will time out in 15 seconds. You can give your own timeout as a parameter, if the timeout is too big, or too small.

There may be some other use cases for this simple extension, too.

Installation

Nuget package

The easiest way is to install the ViewModelAssertions NuGET package

Or by Package Manager Install-Package ViewModelAssertions -Version 1.1.0

From source

You can also download the source (AssertionExtensions project) and add it into your solution directly.

License

Copyright 2020 Antti Konsta Kustaa

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.