test-writing-guide

Guide for writing test code for Unity projects.

Rules

• Before modifying any test file, check if the editor is in Play Mode. If it is, stop it using the unity_play_control tool first.
• Never create .meta files. Unity editor creates them automatically.
• When a test creates a GameObject or instantiates a prefab, add [CreateScene] to the test method (not required if [LoadScene] is already present).
• When adding a test seam to production code (e.g., an internal accessor or a virtual override point to support injection), always wrap it with #if UNITY_INCLUDE_TESTS … #endif so it is excluded from non-test builds:

  #if UNITY_INCLUDE_TESTS
  internal void SetStateForTest(State state) => _state = state;
  #endif
  

Categories

• When implementing tests designed as integration tests, add [Category("Integration")] to the test method.
• When implementing tests designed as visual verification tests, add [Category("VisualVerification")] to the test method.
• When implementing tests designed as acceptance tests (marked (acceptance test) in the test case design), add [Category("Acceptance")] to the test method.
• For test methods that test the internal visibility method, add [Category("Internal")].
• For test methods that depend on animation timing or other timing-sensitive conditions that may cause instability on slow CPUs, add [Category("IgnoreCI")].
• For test methods that specify the GameViewResolution attribute, add [Category("IgnoreCI")].

Multi-frame tests

When a game mechanic across frames (e.g., playing a card and waiting for its resolution), wait for the step to finish before asserting — not at a fixed frame count.

await DragCard(Cards[1], Enemies[0]);
while (battleDirector.IsPlaying) // wait until the played action fully resolves
    await Awaitable.NextFrameAsync();
Assert.That(battleState.Enemies[0].Hp, Is.LessThan(hpBefore));

• To confirm step completion, use a production-side state machine or a "busy" signal (IsPlaying, coroutine flag, etc.). Do not use a fixed number of frames or WaitForSeconds.
• When UniTask is available, UniTask.WaitUntil and UniTask.WaitUntilValueChanged are alternatives to the while loop:

  await UniTask.WaitUntil(() => isActive == false);
  await UniTask.WaitUntilValueChanged(this, x => x.isActive);
  

• When an operation triggers a deferred Destroy or UI rebuild, advance one extra await Awaitable.NextFrameAsync() before asserting on the new hierarchy.

UI Tests

Layout assertion tests: verify UI layout with deterministic assertions

When a layout requirement is expressible as a deterministic assertion (the element is within the screen, elements do not overlap, text does not overflow its container), write it as a layout assertion test (an integration test), not a visual verification test. Displayed content (card data, text length, item count) is a test input: the pass criterion never varies with it. Leave to visual verification what does not suit a strict assertion: color, positional relationships like "A is to the right of B", on-screen position, and typography (font size, font style, font family) are design intent likely to change, and legibility (text/background contrast) is impractical to assert. Reasons:

• Deterministic pass/fail: boolean assertions run unattended in CI without a human reading screenshots.
• Pins the specific bug: an overlap assertion names the two elements; a screenshot cannot.
• Do NOT add a visual verification test for the same property — verify each layout property in exactly one layer.

Choose the implementation means by what the condition is about:

• Rect comparison — Is.WithinScreen (within-screen bounds), Is.FullyWithin(container) (containment in a parent), Is.Not.Overlapping (overlap between elements)
• Text overflow — Is.Not.TextOverflowing (preferred/rendered size exceeds the rect, or characters are truncated)
• Raycast reachability — GameObjectFinder with reachable: true (optionally with a paginator) proves the element is on screen and not covered by another element; use it when the condition is "the user can actually reach this element"

Before asserting, settle layout with Canvas.ForceUpdateCanvases() then await Awaitable.NextFrameAsync() — the former rebuilds pending layout/graphic geometry (rect sizes, text metrics); the latter waits for a real render pass, which is what a raycast reachability check needs, since a newly activated/deactivated Graphic's CanvasRenderer.depth stays unset until then and GraphicRaycaster silently skips any candidate whose depth == -1 — ForceUpdateCanvases() alone does not assign it.

See test-helper.md → Layout constraints for the constraint API (Is.WithinScreen / Is.FullyWithin / Is.Not.Overlapping / Is.Not.TextOverflowing).

Use GameObjectFinder instead of GameObject.Find

When finding a GameObject that the user interacts with, always use TestHelper.UI.GameObjectFinder instead of UnityEngine.GameObject.Find, Object.FindFirstObjectByType, Object.FindAnyObjectByType, and Object.FindObjectOfType. Reasons:

• Timing safety: polls until the object appears, so tests pass even when GameObjects are instantiated asynchronously or on the next frame
• Reachability and interactability: verifies the object is actually reachable by the user and (optionally) interactable — matching real user experience
• Blocking check: reachable: true (default) naturally catches elements hidden behind a modal or overlay — which is often the bug being caught
• Actionable failures: throws TimeoutException with a clear message; GameObject.Find silently returns null and causes a confusing NullReferenceException later

Use Operators instead of direct event invocation

When reproducing user actions, always use uGUI operators (e.g., UguiClickOperator, UguiTextInputOperator in TestHelper.UI.Operators namespace) instead of directly calling button events or setting field values. Reasons:

• Correct event simulation: operators go through Unity's EventSystem and input pipeline, exercising the same code path as a real user interaction
• Reachability-gated: test fails if a UI element is disabled or hidden
• Simpler test code: no need to look up components or call internal methods; just find the GameObject and operate it

// NG — bypasses Unity's event pipeline
button.GetComponent<Button>().onClick.Invoke();
inputField.GetComponent<InputField>().text = "12345";
scene.OnConfirmClicked();

// OK — goes through the proper UI event path
await new UguiClickOperator().OperateAsync(button);
await new UguiTextInputOperator().OperateAsync(inputField, "12345");

Verify modal/overlay blocking

A modal or overlay must block interaction with elements behind it. Test from two angles:

• Behavioural (preferred): attempt to reach a background element via GameObjectFinder with reachable: true (default) while the overlay is open — the finder throws TimeoutException, confirming blockage. Repeat with the overlay dismissed to confirm reachability restores.
• Structural: assert the backdrop intercepts raycasts: Assert.That(background.GetComponent<Image>().raycastTarget, Is.True) (or canvasGroup.blocksRaycasts).

When a decorative full-screen element should not block (e.g., a background image), annotate it with NonBlockingAnnotation so GameObjectFinder skips it (see test-helper-ui.md).

Visual verification tests

When implementing a visual verification test (a test designed to verify on-screen rendering via screenshot and image analysis):

1. Take a screenshot using [TakeScreenshot] or ScreenshotHelper.TakeScreenshotAsync() (see test-helper.md).
2. Add [Description("After running this test, verify the screenshots from the following perspectives: <verification aspects>")] to the test method. The verification aspects are taken directly from the Image analysis by saved screenshot column in the test case design. List only aspects suited to visual verification (legibility, contrast, positional relationships, typography, visual state representation, rendering quality) — do NOT list mechanically assertable facts such as a panel's activeSelf or exact text content; assert those in integration tests instead.
3. Add [Category("VisualVerification")] to the test method.
4. You can omit writing Assert statements.

When a designed visual verification test shares its test condition with a designed layout assertion test, you may implement both as a single test method: take the screenshot in the layout assertion test, apply steps 2–3 to it, and keep the layout assertions (step 4 does not apply).

Resources

Read the appropriate resource file based on the situation:

• Before writing or modifying any test code file: Read ${CLAUDE_SKILL_DIR}/resources/unity-test-framework.md
• Before writing or modifying any test code file: Read ${CLAUDE_SKILL_DIR}/resources/test-helper.md
• Before writing or modifying UI tests with TestHelper.UI namespace API (e.g., GameObjectFinder, Monkey): Read ${CLAUDE_SKILL_DIR}/resources/test-helper-ui.md
• Before writing or modifying performance tests (com.unity.test-framework.performance, [Performance], Measure.*): Read ${CLAUDE_SKILL_DIR}/resources/unity-test-framework-performance.md