mstest-wpf-testing-patterns

# WPF Testing Patterns Agent protects WPF behavior with fast tests around view models, commands, validation, and service boundaries instead of relying on broad UI automation. ## When to Use | Condition | Use | |---|---| | Agent adds or changes view-model behavior in a WPF feature. | Agent uses this skill. | | Agent needs regression coverage for commands, property changes, or validation. | Agent uses this skill. | | Agent needs MSTest v4 coverage without launching full WPF windows. | Agent uses this skill. | ## When Not to Use | Condition | Use | |---|---| | Agent changes only pure styling with no state or command behavior. | Agent uses manual visual verification. | | Agent needs a broad test-suite generation workflow. | Agent uses a dedicated testing bundle. | | Agent focuses on UI automation for rendering-only issues. | Agent limits work to targeted UI checks. | ## Required Inputs | Input | Required | Notes | |---|---|---| | Target class | Yes | Target identifies the view model or service under test. | | Expected interactions | Yes | Interactions identify commands, notifications, and collaborator effects. | | Test doubles | No | Doubles identify fakes or mocks for collaborators. | | Coverage goals | No | Goals identify risky paths and boundary conditions such as null input, empty collections, and selection changes. | | UI smoke scope | No | Scope identifies any small rendering checks outside unit tests. | ## Workflow | Step | Agent action | Output | Test | Pass | |---|---|---|---|---| | 1. Isolate testable logic | Agent extracts dialogs, navigation, dispatcher work, and transport dependencies behind interfaces. | Test seam map | Agent instantiates the target in a test. | The target runs without WPF runtime dependencies. | | 2. Use MSTest v4 | Agent places tests in an MSTest v4 project that matches repository conventions. | Test project | Agent runs targeted tests. | Test discovery succeeds. | | 3. Use simple fakes | Agent uses deterministic fakes for straightforward collaborators and uses mocks only where interaction verification needs them. | Test doubles | Agent inspects collaborator effects. | Tests read behavior directly and stay easy to diagnose. | | 4. Drive public behavior | Agent exercises commands, properties, and validation through the public surface instead of private helpers. | Behavior tests | Agent runs the target tests. | Failures map to user-visible behavior. | | 5. Cover async and error flows | Agent tests busy flags, cancellations, failed service calls, and recovery state. | Async-path tests | Agent forces failures and cancellations. | The target resets state correctly after non-happy paths. | | 6. Limit UI automation | Agent reserves UI automation for WPF-only concerns such as keyboard traversal, accessibility, or virtualization quirks. | UI smoke scope | Agent reviews the scope. | UI automation remains small and justified. | ## Common Pitfalls | Pitfall | Fix | |---|---| | Agent tests private helpers instead of user-visible behavior. | Agent drives tests through public commands and properties. | | Agent keeps WPF globals inside view models. | Agent extracts those concerns behind interfaces. | | Agent stops at null checks and shallow assertions. | Agent asserts state transitions and collaborator effects. | | Agent uses UI automation for every rule. | Agent keeps UI automation for WPF-specific concerns only. | ## Verification Matrix | Test | Run | Pass | |---|---|---| | Targeted tests | `dotnet test [test-project].csproj` | All targeted tests pass | | Coverage check | `dotnet test [test-project].csproj --collect:"XPlat Code Coverage"` when the project already uses coverage | Coverage run succeeds | | Manual smoke pass | Small keyboard or binding pass when required | No WPF-only regression remains | ## Verification Checklist - [ ] Agent tests commands through their public command surface. - [ ] Agent asserts property changes, validation states, and collaborator effects. - [ ] Agent covers one failure or cancellation path for each changed behavior. - [ ] Agent keeps most coverage outside UI automation. - [ ] Agent uses MSTest v4 conventions. ## Additional source coverage The selected version is the preferred starting point by the recorded date/context basis. Distinct source coverage is retained in the scoped references; do not apply superseded or conflicting defaults automatically. - [wpf-testing-patterns-alternative-1](references/contexts/wpf-testing-patterns-alternative-1/guide.md)