In this post I wrote about the use of app settings in Asp.Net Core. One thing that I didn’t cover at the time was the fact that, as an extension library, the configuration extensions weren’t very easy to include in unit tests. Of course the intention is that you read the configuration at the start, pass through a model class and no mocking is required.
However, sometimes you’ll find yourself wanting to mock out a particular setting. Before I get into this, this post is heavily based on this article which describes the same process.
The following is a code sample using Moq:
var configuration = new Mock<IConfiguration>();
var configurationSection = new Mock<IConfigurationSection>();
configurationSection.Setup(a => a.Value).Returns("testvalue");
configuration.Setup(a => a.GetSection("TestValueKey")).Returns(configurationSection.Object);
This will cause any call to get the app settings key “TestValueKey” to return “testvalue”. As is stated in the linked article, whilst GetValue is an extension method, GetSection is not, but is (internally) called by GetValue.
Entity Framework Core 2.1 comes with a nifty little feature: an In Memory Database setting. What this means, is that with a single option setting, your tests can interact directly with the database (or at least EF’s impression of the database) but not actually touch any physical database. In other words, you can write unit tests for data access; an example:
DbContextOptions<ApplicationDbContext> options = new DbContextOptionsBuilder<ApplicationDbContext>()
using (var context = new ApplicationDbContext(options))
ResourceCategory resourceCategory = new ResourceCategory()
Name = "TestCategory"
To just quickly explain what this is doing: we have a DbContext called ApplicationDbContext and we’re building a set of options on top of that context. We’re then instantiating the context and cleaning the in memory database. Finally, we’re adding a new piece of data to the context and then asserting that it has been added.
Told you it was nifty.
But what about if you’re still using Entity Framework 6?
Glad you asked.
Out of the box, EF does not come with this kind of functionality; however, I recently came across (and contributed) to a NuGet library that provides just such a facility. It provides a wrapper for both Moq and Nsubstitute. The GitHub Repo is here.