DataSourceGeneratorAttribute display name formatting for classes

[VMelnalksnis]

As far as I can tell, TUnit just uses the argument type name in class names when a DataSourceGeneratorAttribute is used on a class. That means that I have to create a subclass for each fixture in order for it to have a different name in the test explorer, and it limits how the name can be formatted since it has to be a valid class name. In NUnit it is possible to change the display name with TestFixtureData.SetArgDisplayNames, maybe something similar is possible in TUnit?

[thomhurst]

Can you try in 0.1.1079.

In your custom DataSourceGeneratorAttribute, implement the interface ITestDiscoveryEvent. Then on the DiscoveredTestContext object given to you, you can call SetDisplayName. You can then set it based on whatever logic you like.

For example:

    [Test]
    [MyGenerator]
    public async Task PasswordTest(string password)
    {
        await Assert.That(TestContext.Current!.TestDetails.DisplayName).IsEqualTo("PasswordTest(REDACTED)");
    }
    
    public class MyGenerator : DataSourceGeneratorAttribute<string>, ITestDiscoveryEvent
    {
        public override IEnumerable<string> GenerateDataSources(DataGeneratorMetadata dataGeneratorMetadata)
        {
            yield return "Super Secret Password";
        }

        public void OnTestDiscovery(DiscoveredTestContext discoveredTestContext)
        {
            discoveredTestContext.SetDisplayName($"{discoveredTestContext.TestDetails.TestName}(REDACTED)");
        }
    }

[VMelnalksnis]

I'm not sure that's quite it - this changes the name of each test case instead of the class.
Here's an example of what I have in NUnit now:

Where OpenApiTests is the class and 12.20-bookworm is the display name of the fixture passed to the class. Using your what you suggested changes the name of each test case, ApiDefinition_ShouldBeExpected(/swagger/v1/swagger.json) in this case. It also overwrites the test case parameter values. What I'd like to format is the 12.20-bookworm value in this example, instead of it just using the type name.

[thomhurst]

Got ya. Try this then:

Create a class inheriting from ArgumentDisplayFormatter. Here you define whether you support formatting specific objects, and then also the converting to a string value.

e.g.

public class MyFormatter : ArgumentDisplayFormatter
{
    public override bool CanHandle(object? value)
    {
        return value is SomeFixture;
    }

    public override string FormatValue(object? value)
    {
        var fixture = (SomeFixture) value;
        return fixture.SomeProperty;
    }

Then apply that to your test/class/assembly with the ArgumentDisplayFormatter<> attribute.

E.g.

[ArgumentDisplayFormatter<MyFormatter>]
public class MyTests { ... }

And that should do it.

[VMelnalksnis]

Thanks, that works! Some related feedback - initially no tests were discovered, I'm guessing because my formatter was throwing an exception. However, there was no visible error in build output/IDE. Would it be possible to somehow surface exceptions such as this so that there is no need to guess what went wrong?