stride3d/stride · error · InvalidOperationException

[UITest] class must implement IUITest.

Error message

[UITest] class {chosen.FullName} must implement IUITest.

What it means

After choosing the [UITest] class, LoadTest verifies it implements IUITest. If the annotated class does not implement the interface, it throws InvalidOperationException with the class's full name. The attribute alone is not sufficient; the type must be instantiable as an IUITest to be run.

Solutions

1. Make the annotated class implement IUITest and rebuild.
2. Remove [UITest] from classes that are not actual runnable tests.
3. Point --test-name at the correct test class instead of the mis-annotated one.
4. Add a compile-time check (e.g. where T : IUITest pattern or unit test asserting all [UITest] types implement IUITest).

Example fix

// before
[UITest]
public class SmokeTest { public void Run(Context ctx) { ... } }
// after
[UITest]
public class SmokeTest : IUITest { public void Run(Context ctx) { ... } }

var bad = asm.GetTypes()
    .Where(t => t.GetCustomAttribute<UITestAttribute>() is not null && !typeof(IUITest).IsAssignableFrom(t))
    .ToList();
if (bad.Count > 0) throw new InvalidOperationException($"[UITest] types not implementing IUITest: {string.Join(", ", bad.Select(t => t.FullName))}");

try { test = LoadTest(dll, testName); }
catch (InvalidOperationException ex) { Console.Error.WriteLine(ex.Message); return 1; }

When it happens

Trigger: Annotating a class with [UITest] that does not implement IUITest (interface dropped during refactor, or attribute applied to a helper/model class by mistake).

Common situations: Renaming or refactoring removed the IUITest base; a developer copies [UITest] onto the wrong class; a partial implementation class only satisfies the interface in another assembly.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• No [UITest] class found in
• No [UITest] class named
• Multiple [UITest] classes in
• The assetUpgraderType must implement IAssetUpgrader…
• compilationContext should inherit from ICompilationContext

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/3dfaf47ea6153758. Report an issue: GitHub.

Appendix: source

Thrown at sources/editor/Stride.GameStudio.AutoTesting/UITestHost.cs:174

            throw new InvalidOperationException($"No [UITest] class found in '{testDllPath}'.");

        Type chosen;
        if (testClassName is not null)
        {
            chosen = candidates.FirstOrDefault(t => t.Name == testClassName || t.FullName == testClassName)
                ?? throw new InvalidOperationException($"No [UITest] class named '{testClassName}' in '{testDllPath}'. Available: {string.Join(", ", candidates.Select(t => t.FullName))}");
        }
        else if (candidates.Count == 1)
        {
            chosen = candidates[0];
        }
        else
        {
            throw new InvalidOperationException($"Multiple [UITest] classes in '{testDllPath}'; pass --test-name to select. Available: {string.Join(", ", candidates.Select(t => t.FullName))}");
        }

        if (!typeof(IUITest).IsAssignableFrom(chosen))
            throw new InvalidOperationException($"[UITest] class {chosen.FullName} must implement IUITest.");

        return (IUITest)Activator.CreateInstance(chosen)!;
    }

    private void RunTest(IUITest test, Context ctx)
    {
        Task.Run(async () =>
        {
            var status = "ok";
            object? exceptionInfo = null;
            try
            {
                await test.Run(ctx);
            }
            catch (Exception ex)
            {
                status = "error";
                exceptionInfo = SerializeException(ex);

View on GitHub (pinned to 96fad776d2)