gum-unit-tests

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name: gum-unit-tests description: Writing unit tests in the Gum repo. Triggers: tests in Gum.ProjectServices.Tests, Gum.Cli.Tests, or any other Gum test project.

Gum Unit Test Reference

Test Projects

Project	Location	What it tests
MonoGameGum.Tests	MonoGameGum.Tests/	Default project for new tests. MonoGame runtime, Forms controls, rendering, localization, data types — anything not specific to V2/V3 visuals or integration
Gum.ProjectServices.Tests	Tests/Gum.ProjectServices.Tests/	Headless services: error checking, codegen, font generation, project loading
Gum.Cli.Tests	Tests/Gum.Cli.Tests/	CLI command exit codes and output
MonoGameGum.Tests.V2	Tests/MonoGameGum.Tests.V2/	Tests specific to V2 default visuals
MonoGameGum.Tests.V3	Tests/MonoGameGum.Tests.V3/	Tests specific to V3 default visuals
MonoGameGum.IntegrationTests	Tests/MonoGameGum.IntegrationTests/	Requires a real GraphicsDevice: content loading, renderer teardown, full GumService lifecycle
RaylibGum.Tests	Tests/RaylibGum.Tests/	raylib runtime (incl. the #if RAYLIB branches of the source-shared GueDeriving/*Runtime.cs)
SkiaGum.Tests	Tests/SkiaGum.Tests/	Skia runtime and shape runtimes
Gum.ProjectServices.SkiaGum.Tests	Tests/Gum.ProjectServices.SkiaGum.Tests/	SkiaGum-backed SVG export (SkiaGumSvgExportService, the service behind gumcli svg / tool File ▸ Export); drives SKSvgCanvas headlessly

When in doubt, put tests in MonoGameGum.Tests/. Only use V2/V3 projects for tests that exercise visual-version-specific behavior.

SkiaGum.Tests runs in CI as a blocking suite (#3233) — it renders into an in-memory CPU raster SKSurface, so it is fully headless despite the name. A red Skia test now fails the job like any other Bucket-A suite.

RaylibGum.Tests runs in CI as a blocking Windows suite (#3250). raylib's InitWindow needs an OpenGL 3.3 context the GPU-less runners lack; the Windows job supplies it via Mesa's llvmpipe software GL (dropped in next to the test binaries before the suite runs), so the tests run headless and a red raylib test now fails the job like any other Bucket-A suite. (#3233's earlier macOS probe hung at GLFW/Cocoa window creation — Win32 window creation is not main-thread-coupled, which is why Windows works.) A green CI run now does cover raylib — including the #if RAYLIB branches of a source-shared GueDeriving/*Runtime.cs — so the old mandatory local pre-merge run is no longer required; still update any assertion that pins old behavior when you change raylib-covered code. (Issue #3234: #3183 changed the raylib stroke-width PreRender but left the suite asserting the pre-#3183 value; back then CI didn't run raylib, so it shipped red — now it would be caught.)

Key Rules

• Always use Shouldly — never xUnit Assert. Alphabetize test methods within a class.
• Disable parallel execution in every test project ([assembly: CollectionBehavior(DisableTestParallelization = true)]) — Gum uses global singletons.
• Use named parameters for boolean literals.

Test at production defaults

When a feature's tests disable a production default for isolation (e.g. LoaderManager.Self.CacheTextures = false), remember that default is on in real apps — so any code path that only runs with it on is left untested. Treat "this test turns a production default off" as a smell: keep at least one test that exercises the path at the production default. (A raylib font regression survived review because every font test ran with caching off, which made a new cache-hit branch dead code.)

Headless Tests (ProjectServices, MonoGameGum.Tests.V2)

Read BaseTestClass before adding setup — it handles singleton init, a ready-made GumProjectSave, and Dispose cleanup. Don't repeat that in subclasses.

Every StateSave must have ParentContainer set — GetValueRecursive traverses via that field and silently misbehaves or throws when it is null. Use ScreenSave for standalone state tests (no base type, no StandardElementsManager fallback).

InternalsVisibleTo is set up in Gum.ProjectServices.csproj for Gum.ProjectServices.Tests — internal members are directly accessible.

WPF-touching tool code (GumToolUnitTests) needs an STA thread

xUnit's runner is MTA, but WPF FrameworkElements (MenuItem, Menu, ComboBox, …) throw InvalidOperationException: The calling thread must be STA when constructed. If a tool class news up a WPF control — often a ViewModel building right-click MenuItems in its constructor — build it inside a RunOnSta(() => { ... }) helper that runs the body on an ApartmentState.STA thread and rethrows. Copy the helper from MenuStripManagerTests / RenameManagerTests; there is no shared base for it.

Verify the real construction blocker empirically before designing around an assumed one. A quick throwaway probe (construct the object, see what actually throws) beats reasoning: e.g. BitmapFrame PNG decode and most non-control VM constructors run fine on MTA, so the blocker is usually the WPF control, not the singleton/resource you suspected.

Plugin/DI composition tests (GumToolUnitTests)

AllPluginsCompositionTests composes every tool plugin through MEF the way PluginManager.LoadPlugins does, and ServiceProviderCompositionSpikeTests resolves the bridged services from the real Builder.cs container. Two reusable techniques live there:

• Stub anything headlessly without running its constructor. RuntimeHelpers.GetUninitializedObject(type) fabricates a concrete instance (even a heavy WinForms/WPF host singleton) with no ctor call; a Moq proxy covers interfaces/abstract types. Composition/DI only needs the dependency to exist as the right type, so this avoids STA/graphics setup entirely. (Run the composition on RunOnSta regardless — some plugin constructors still touch WPF.)
• Satisfy not-yet-drained plugins' direct Locator.GetRequiredService<T>() ctor calls with a catch-all IServiceProvider registered via Locator.Register(...); remove it in Dispose (Locator has no Unregister — RenameManagerTests shows the reflection teardown).

Keep the MEF batch an explicit mirror of LoadPlugins (not a catch-all export provider) so a plugin gaining an unbridged [ImportingConstructor] dependency turns the test red — that regression signal is the whole point. See the gum-tool-plugins skill for keeping PluginBridgedServiceTypes.All in sync during drains.

Integration Tests (MonoGameGum.IntegrationTests)

Use this project for anything requiring a real GraphicsDevice. Each test creates a minimal nested Game subclass, calls game.RunOneFrame() to trigger Initialize, then asserts. See Tests/MonoGameGum.IntegrationTests/MonoGameGum/GumServiceUnitTests.cs for the established pattern. Always call LoaderManager.Self?.DisposeAndClear() in the Game.Dispose override to prevent state leaking across tests via the singleton.