bunit.generators

bUnit Generators

This package contains source generators for bUnit, to make it easier and more convenient to write tests.

AddStub Generator

This generator adds the ability to automatically generate stubs for a given type with no setup involved. The generator sits on top of the already present AddStub method. This comes in handy, when dealing with 3rd party components that might need an extensive setup. Here a small example:

Given the following component

<ThirdPartyText Text="@count" />
<button @onclick="IncrementCount">Increase by one</button>
@code {
 private int count;
 
 private void IncrementCount()
 {
	 count++;
 }
}

If ThirdPartyText is a 3rd party component, that needs a lot of setup, it might be easier to just stub it out:

[Fact]
public void Text_button_gets_initial_count()
{
    // This call will automatically generate a stub for the ThirdPartyButton component
    // with the name "ThirdPartyButtonStub"
    ComponentFactories.AddStub<ThirdPartyText>();
    var cut = Render<Counter>(@<Counter />);
    
    cut.Find("button").Click();
    
    // Retrieves the stub from the render tree and checks if the text is "1"
    cut.FindComponent<ThirdPartyTextStub>().Instance.Text.Should().Be("1");
}

Setup

To use the generator, the Interceptor feature has to be used inside the csproj file:

<Project Sdk="Microsoft.NET.Sdk">
	<PropertyGroup>
		<TargetFramework>net8.0</TargetFramework>
		<!-- This line is required to enable the generator and interceptor -->
		<InterceptorsPreviewNamespaces>$(InterceptorsPreviewNamespaces);Bunit</InterceptorsPreviewNamespaces>

This limits the usage to .NET 8 and above.

ComponentStubAttribute

This generator adds the ability to automatically generate stubs for a given type via an attribute. The general setup for the given component above looks like this:

namespace MyTest;

public class FeatureTest : BunitContext
{
    [Fact]
    public void Test()
    {
        ComponentFactories.Add<ThirdPartyText, ThirdPartyStub>();
        ...
    }    
}

[ComponentStub<ThirdPartyText>)]
internal partial class ThirdPartyStub { }

Current limitations of this approach:

• The stubbed type is not allowed to be nested inside the test class.