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control-api-tests

Write xUnit unit tests for new public APIs on WinForms controls and components.

1.2k|337|Updated Oct 13, 2022
Search Tags:#csharp#test conventions#winforms#Unit testing#XUnit#DotNet#control api
One-click install
npx skills add https://github.com/dotnet/dotnet --skill control-api-tests
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: control-api-tests
Source: https://github.com/dotnet/dotnet/tree/main/src/winforms/.github/skills/control-api-tests
Command: npx skills add https://github.com/dotnet/dotnet --skill control-api-tests

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Adding a new public property, method, or event to a WinForms control requires a specific, repeatable set of unit tests, and missing categories like handle-state verification or event idempotency leads to incomplete coverage and CI failures.

Core Features & Use Cases

  • Standardized Test Patterns: Provides naming conventions, the SubControl pattern for testing protected members, and data attributes like [WinFormsTheory] and [EnumData] for STA-thread-aware xUnit tests.
  • Required Test Categories: Covers default values, set/get round-trips with and without a native handle, event firing and idempotency, OnXxx virtual method invocation, and ICommand binding lifecycles.
  • CI Pitfall Guidance: Explains xUnit v3 analyzer rules such as passing CancellationToken to async calls and enabling #nullable context that fail CI builds.
  • Use Case: When you add a new DialogResult-style property to a WinForms control, use this Skill to generate the full checklist of tests including handle-state assertions and event subscription/unsubscription verification.

Quick Start

Write the complete set of unit tests for a new public property on a WinForms control following the control-api-tests conventions.

Frequently Asked Questions about control-api-tests

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I write unit tests for a new WinForms control property?▼

Create tests covering the default value, set/get round-trips with and without a native handle, event firing on value change, and event idempotency. Use [WinFormsFact] or [WinFormsTheory] attributes and always dispose controls with using declarations.

How to test protected OnXxx methods in WinForms controls?▼

Create a private nested subclass named Sub{ControlName} inside the test class that re-exposes protected members using public new. This lets tests invoke OnXxx methods directly and verify event raising behavior.

Why does my WinForms test fail CI but pass local dotnet build?▼

CI runs xUnit v3 analyzers as errors, including CA2016 requiring a CancellationToken in async calls and CS8632 requiring a #nullable context for nullable annotations. Verify with build.cmd instead of a single-project dotnet build.

What test attributes does the WinForms test project use?▼

The project uses [WinFormsFact] and [WinFormsTheory], which are STA-thread-aware xUnit attributes required for COM interop and UI operations. Data attributes like [BoolData], [EnumData<T>], and [NewAndDefaultData<EventArgs>] generate test values.

When should WinForms tests verify handle state?▼

Verify Assert.False(control.IsHandleCreated) in default-value and no-handle round-trip tests to ensure property access does not force handle creation. For with-handle tests, force handle creation and assert no unexpected Invalidated, StyleChanged, or HandleCreated events fire.

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