bunit-test-migration

bUnit Test Migration Skill (Beta → 2.x)

This skill provides guidance for migrating test files from the deprecated bUnit 1.0.0-beta-10 API to bUnit 2.5.3 stable API. Use this when you encounter test files using the old TestComponentBase, <Fixture>, or <SnapshotTest> patterns.

When to Apply

Apply this skill when a .razor test file contains any of these patterns:

• @inherits TestComponentBase
• <Fixture Test="...">
• <ComponentUnderTest>
• <SnapshotTest>
• void MethodName(Fixture fixture)

Transformation Rules

1. Change Inheritance

- @inherits TestComponentBase
+ @inherits BunitContext

2. Remove Wrapper Elements

Remove these XML elements entirely (keep only the component inside):

- <Fixture Test="TestName">
-     <ComponentUnderTest>
          <MyComponent Parameter="value" />
-     </ComponentUnderTest>
- </Fixture>

3. Convert Test Methods

- void TestMethodName(Fixture fixture)
+ [Fact]
+ public void ComponentName_Scenario_ExpectedResult()

4. Replace Component Access

- var cut = fixture.GetComponentUnderTest();
+ var cut = Render(@<MyComponent Parameter="value" />);

5. Convert Snapshot Tests

- <SnapshotTest Description="renders correctly">
-     <TestInput>
-         <MyComponent />
-     </TestInput>
-     <ExpectedOutput>
-         <div>expected html</div>
-     </ExpectedOutput>
- </SnapshotTest>
+ [Fact]
+ public void MyComponent_Default_RendersCorrectly()
+ {
+     var cut = Render(@<MyComponent />);
+     cut.MarkupMatches(@<div>expected html</div>);
+ }

Complete Example

Before

@inherits TestComponentBase

<Fixture Test="ShouldClickButton">
    <ComponentUnderTest>
        <Button OnClick="OnClick">Click me</Button>
    </ComponentUnderTest>
</Fixture>

@code {
    int ClickCount = 0;

    void ShouldClickButton(Fixture fixture)
    {
        var cut = fixture.GetComponentUnderTest();

        cut.Find("button").Click();

        ClickCount.ShouldBe(1);
    }

    void OnClick() => ClickCount++;
}

After

@inherits BunitContext

@code {
    int ClickCount = 0;

    [Fact]
    public void Button_Click_IncrementsCounter()
    {
        var cut = Render(@<Button OnClick="OnClick">Click me</Button>);

        cut.Find("button").Click();

        ClickCount.ShouldBe(1);
    }

    void OnClick() => ClickCount++;
}

Test Naming Convention

Pattern: ComponentName_Scenario_ExpectedResult

Component	Scenario	Result	Test Name
Button	Click	InvokesHandler	Button_Click_InvokesHandler
DataList	EmptySource	ShowsEmptyTemplate	DataList_EmptySource_ShowsEmptyTemplate
GridView	WithData	RendersRows	GridView_WithData_RendersRows

Special Patterns

Multiple Tests in One File

Each <Fixture> block becomes a separate [Fact] method:

@inherits BunitContext

@code {
    [Fact]
    public void Component_FirstScenario_ExpectedResult() { ... }

    [Fact]
    public void Component_SecondScenario_ExpectedResult() { ... }
}

Tests with Services

@code {
    [Fact]
    public void Component_WithService_Works()
    {
        Services.AddSingleton<IMyService>(new FakeService());

        var cut = Render(@<MyComponent />);
    }
}

Authentication Tests

@code {
    [Fact]
    public void SecureComponent_AuthenticatedUser_ShowsContent()
    {
        var authContext = this.AddTestAuthorization();
        authContext.SetAuthorized("TestUser");
        authContext.SetRoles("Admin");

        var cut = Render(@<SecureComponent />);
    }
}

Tests Requiring New TestContext

For tests that need isolated context (e.g., multiple renders):

@code {
    [Fact]
    public void Component_MultipleRenders_WorksCorrectly()
    {
        using var ctx = new Bunit.TestContext();

        var cut1 = ctx.Render(@<MyComponent Value="1" />);
        var cut2 = ctx.Render(@<MyComponent Value="2" />);

        cut1.Find("span").TextContent.ShouldBe("1");
        cut2.Find("span").TextContent.ShouldBe("2");
    }
}

Tests with xUnit Logger (Optional)

For debugging complex tests, you can optionally enable xUnit logging:

@using Microsoft.Extensions.Logging

@code {
    private ILogger<MyTest> _logger;

    public MyTest(ITestOutputHelper output) : base(output)
    {
    }

    [Fact]
    public void Component_ComplexScenario_WorksAsExpected()
    {
        _logger = Services.GetService<ILogger<MyTest>>();
        _logger?.LogInformation("Starting test");

        var cut = Render(@<MyComponent />);

        _logger?.LogDebug("Component rendered");

        // Test assertions...
    }
}

Note: Only add logging when diagnostic output is helpful. Most tests should remain simple without logging.

Quick Reference Table

Old Pattern	New Pattern
@inherits TestComponentBase	@inherits BunitContext
<Fixture Test="Name">	Remove
<ComponentUnderTest>	Remove
<SnapshotTest>	[Fact] method with MarkupMatches()
void Name(Fixture fixture)	[Fact] public void Name()
fixture.GetComponentUnderTest()	Render(@<Component />)
fixture.GetComponentUnderTest<T>()	Render<T>(@<Component />)

Verification

After migrating a file, verify with:

# Build check
dotnet build src/BlazorWebFormsComponents.Test --no-restore

# List discovered tests
dotnet test src/BlazorWebFormsComponents.Test --list-tests --filter "FullyQualifiedName~ComponentName"

# Run tests
dotnet test src/BlazorWebFormsComponents.Test --filter "FullyQualifiedName~ComponentName"

Common Errors

Error	Cause	Fix
CS0246: TestComponentBase not found	Old inheritance	Change to @inherits BunitContext
CS0103: Fixture does not exist	Old wrapper element	Remove <Fixture> tags
No tests discovered	Missing [Fact] attribute	Add [Fact] to test methods
Method must be public	Private test method	Add public modifier