Testing a .NET Core Library in VS2015
Posted by bsstahl on 2017-01-09 and Filed Under: development
I really enjoy working with .NET Core. I like the fact that my code is portable to many platforms and that the footprint is so much smaller than with traditional .NET applications. Unfortunately, the tooling has not quite reached the level that we expect from a Microsoft finished product (which it isn’t – yet). As a result, there are some additional actions we need to take when setting up our solutions in Visual Studio 2015 to allow us to unit test our code properly. The following are the steps that I currently take to setup and test a .NET Core library using XUnit and Moq. I know that a number of these steps will be done for us, or at least made much easier, by the tooling in the coming months, either by Visual Studio 2017, or by enhancements to the Visual Studio 2015 environments.
- Create the library to be tested in Visual Studio 2015
- File > New Project > .Net Core > Class Library
- Notice that this project is created in a solution folder called ‘src’
- Create a solution folder named ‘test’ to hold our test projects
- Right-click on the Solution > Add > New Solution Folder
- Add a new console application to the test folder as our test project
- Right-click on the ‘test’ folder > Add > New Project > .Net Core > Console Application
- Add a reference to the library being tested in the test project
- Right-click on the test project > Add > Reference > Select the library to be tested
- Install packages needed for unit testing from NuGet to the test project
- Right-click on the test project > Manage NuGet Packages > Browse
- Install ‘xunit’ as our unit test runner
- The current version for .Net Core is ‘2.2.0-beta4-build3444’
- Install ‘dotnet-test-xunit’ to integrate xunit with the Visual Studio test tools
- The current version for .Net Core is ‘2.2.0-preview2-build1029’
- Install ‘Moq’ as our mocking library
- The current version for .Net Core is ‘4.6.38-alpha’
- Edit the project.json of the test library
- Change the “EmitEntryPoint” option to false
- Add “testrunner” : “xunit” node
Some other optional steps include:
- Install the ‘Microsoft.CodeCoverage’ package from NuGet to enable the code coverage tooling
- Install the ‘Microsoft.Extension.DependencyInjection’ package from NuGet to enable DI
- Install the ‘TestHelperExtensions’ package from NuGet to add extensions that assist with writing good unit tests
- Add any additional runtimes that might be needed. Some options are:
- Set ‘Run tests after build’ in Visual Studio so tests run automatically
There will likely be better ways to do many of these things shortly, but if you know a better way now, please let me know via Twitter @bsstahl.
Code Coverage Teaches and Protects
Posted by bsstahl on 2016-10-14 and Filed Under: development
I often hail code coverage as a great tool to help improve your code base. Today, my use of Code Coverage taught me something about the new .NET Core tooling, and helped protect me from having to support useless code for the lifespan of my project.
In the code below, I used a common dependency injection pattern. That is, an IServiceProvider object holding my dependencies is passed-in to my object and stored as a member variable. When a dependency is needed, I retrieve that dependency from the service provider, and then take action on it. Since there is no guarantee that the dependency I need will have been placed in the container, I use some common guard logic to protect my code.
templates = _serviceProvider.GetService<IEnumerable<Template>>();
if ((templates==null) || (!templates.Any(s => s.TemplateType==ContactPage)))
throw new TemplateNotFoundException(TemplateType.ContactPage, string.Empty);
In this code, I first test that I was able to retrieve a collection of Template objects from the service provider, then verify that the type of Template I need is present in the collection. If either is not the case, an exception is thrown.
I had two tests that covered this section of code, one where the collection was not added to the service provider, the other where an empty collection was added. Both tests passed, however, it wasn't until I looked at the results of the Code Coverage that I realized that the 1st test wasn't doing what I thought it was doing. It turns out that there is actually no way to get a null collection object out of the Microsoft.Extensions.DependencyInjection.ServiceProvider object I am using for my .NET Core apps. That provider simply returns an empty collection if there isn't one in the container. Thus, my check for null was never matched and that branch of code was never executed.
Based on this new knowledge of the behavior of the IServiceProvider, I had a few options. I could:
- Rewrite my test to check for an empty collection. This option seems redundant to me since my check to see if the container holds the template I need is really what I care about.
- Leave the code as-is just in case the behavior of the container changes, accepting that I have what is currently unnecessary and untestable code in my application. I considered this option but it seems to me that a better defense against the unlikely event of a breaking change in the IServiceProvider implementation is described below in option 3.
- Create a new test that verifies the behavior on the ServiceProvider that an empty collection is returned if no collection is supplied to the container. I am not a big fan of this option since it requires me to test OPC (other people's code), and because the risk of this type of breaking change is, in my opinion, extremely low.
- Remove the guard code that tests for null and the test that supports it. Since the code is completely unnecessary, the test itself is redundant because it is, essentially identical to the test verifying that the template I need is in the collection.
I'm sure you've guessed by now that I selected option 4. I removed the guard code and the test from my solution. In doing so, I removed dead code that served no purpose, but would have to be supported through the life of the project.
For those who might be thinking something similar to, "It's nice that the coverage tooling helped you learn about your code, but using Code Coverage as a metric is actually a bad idea so I won't use Code Coverage at all", I'd like to remind you that any tool, such as a hammer or a car, can be abused. That doesn't mean we don't continue to use them, we just make certain that we use them properly. Code Coverage is a horrible way to measure a development team or effort, but it is an outstanding tool and should be used by the development team whenever possible to discover things about the code base.
Code Sample for My TDD Kickstart Sessions
Posted by bsstahl on 2012-02-13 and Filed Under: development
The complete, working application for my .NET TDD Kickstart sessions can be found here.
Unzip the files into a solution folder and open the Demo.sln solution in a version of Visual Studio 2010 that has Unit Testing capability (Professional, Premium or Ultimate). Immediately, you should be able to compile the whole solution, and successfully execute the tests in the Bss.QueueMonitor.Test and Bss.Timing.Test libraries.
To get the tests in the other two test libraries (Bss.QueueMonitor.Data.EF.Test & Bss.QueueMonitor.IntegrationTest) to pass, you will need to create the database used to store the monitored data in the data-tier and integration tests, and enable MSMQ on your system so that a queue to be monitored can be created for the Integration test.
The solution is configured to use a SQLExpress database called TDDDemo. You can use any name or SQL implementation you like, you’ll just need to update the configuration of all of the test libraries to use the new connection. The script to execute in the new database to create the table needed to run the tests can be found in the Bss.QueueMonitor.Data.EF library and is called QueueDepthModel.edmx.sql.
You can install Message Queuing on computers running Windows 7 by using Programs and Features in the Control Panel. You do not need to create any specific queue because the integration test creates a queue for each test individually, then deletes the queue when the test is complete.
If you have any questions or comments about this sample, please start a conversation on Twitter @bsstahl or Contact Me.
.NET TDD Kickstart
Posted by bsstahl on 2012-01-26 and Filed Under: event development
I head out to Fullerton tomorrow for the start of my .NET TDD Kickstart world tour.
In this session, the speaker and the audience will "pair up" for a coding session which will serve as an introduction to Test Driven Development in an Agile environment. We will use C#, Visual Studio and Rhino Mocks to unit test code to be built both with and without dependencies. We will also highlight some of the common issues encountered during TDD and discuss strategies for overcoming them.
I will be presenting this session at numerous venues around the country this year, including, so far:
If you are interested in having me present this or another session at your event, please contact me.
There is much more than an hour’s worth of material to be presented, so instead of trying to rush through everything I want to talk about during this time, I’ve instead taken some questions from this presentation and posted them below. Please contact me if you have any additional questions, need clarification, or if you have an suggestions or additions to these lists.
Update: I have moved the FAQ list here to allow it to be maintained separately from this post.
Developer Ignite in Chandler
Posted by bsstahl on 2009-07-13 and Filed Under: event development
I will be speaking at the Developer Ignite event in Chandler on July 22nd. The topic of my talk will be "Simplicity Through Abstraction" during which I will be giving a very high-level overview of using Dependency Injection as an Inversion-of-Control methodology to create simplicity in software architecture.
While putting my presentation together I have found a number of items that I wanted to include in my presentation, but simply can't due to the obvious constraints of a 5-minute presentation. Some of these items won't even get a mention, others will be mentioned only in passing. I include them here as a list of topics for me to discuss in future posts to this blog. Hopefully this will occur, at least in part, prior to the ignite event so that there will be a set of resources available to those at the event who were previously unfamiliar with these techniques and wish to explore them further.
These topics include:
- IoC Containers
- Dealing with Provider-Specific requirements
- Configuration as a dependency
- Local providers for external dependencies
- Providers as application tiers
- Testing at the provider level
- Top Down Design [Added: 7/12/2009]
If you have a topic that you are particularly interested in, or have any questions about IoC, Dependency Injection, or Providers that you would like me to answer, please use the comments or contact me via Twitter @bsstahl.