unity-test-unit

name	unity-test-unit
description	Use this skill to write Edit Mode and Play Mode unit tests for Unity C# using Arrange-Act-Assert pattern with 10+ test cases per class. Use when the user says "write tests," "unit test this class," "add test coverage," "create tests for X," or wants automated verification of a MonoBehaviour, ScriptableObject, or utility class. Do not use for manual QA test case documentation — use unity-test-case for that.
metadata	{"author":"kuozg","version":"1.3"}

unity-test-unit

Write Unity unit tests: Edit Mode + Play Mode, Arrange-Act-Assert, minimum 10 test cases per class.

Data Categories (ALL THREE REQUIRED — Skipping Any Is a Blocking Failure)

Category 1: Valid Data (Happy Path) — normal inputs → correct output, typical combinations, state transitions with valid triggers.

Category 2: Invalid/Malformed Data (CRITICAL) — test every failure path with same rigor as happy paths:

• Null — null ref for every object parameter, null [SerializeField], null from GetComponent<T>()
• Empty — "", " ", new List<T>(), new T[0], empty ScriptableObject
• Out-of-range — negative where positive expected, int.MaxValue/MinValue, float.NaN, float.PositiveInfinity
• Malformed — wrong enum cast (MyEnum)999, invalid GUID/path, strings with <script>, \0, \n
• Invalid state — before init, after Destroy(), wrong sequence, on disabled/destroyed component
• Duplicate — same item twice, duplicate keys, re-registering listener

Assert specific behavior per failure path: Assert.Throws<ArgumentNullException> (not just Assert.Throws<Exception>), Assert.IsNull, explicit state check. Never assert only "it doesn't crash."

Category 3: Boundary Values (REQUIRED) — at-min · at-max · just-below-min · just-above-max · midpoint. For collections: empty · single-element · first/last element.

Minimum distribution: 3+ valid · 3+ boundary · 4+ invalid = 10+ total per class.

Workflow

1. Read target class: public API, dependencies, state
2. Enumerate Data Contract (BLOCKING GATE) — Before writing any test:
   • Per parameter: list concrete valid values + every invalid variant (null, empty, malformed, out-of-range)
   • Per object state: valid calling states vs invalid states
   • Define contract in 1 sentence per parameter — everything outside = invalid
   • Total must meet: 3+ valid, 3+ boundary, 4+ invalid
3. Classify — Edit Mode vs Play Mode (Play Mode only for coroutines/physics/lifecycle)
4. Write — AAA pattern with [Test] or [UnityTest]
5. Verify — compilation, missing assembly refs, namespace issues
6. Coverage Gate (BLOCKING) — Before done, verify:
   • Every object parameter has null-input test
   • Every string has "" and " " tests
   • Every collection has empty-collection test
   • Every numeric has at-min, at-max, just-outside tests
   • Every method with preconditions has invalid-state test
   • Every failure path asserts specific behavior — not just "doesn't crash"

Rules

• Minimum 10 cases per class (3+ valid, 3+ boundary, 4+ invalid)
• Assert.Throws<T> for expected exceptions — never catch-and-ignore
• Edit Mode preferred; Play Mode only when coroutines/lifecycle required
• Naming: MethodName_Condition_ExpectedResult (e.g. _WithNullInput_, _AtMaxBoundary_)
• Place in Assets/Tests/EditMode/ or Assets/Tests/PlayMode/
• [SetUp]/[TearDown] to prevent state leakage
• [TestCase] for parameterized variants
• Never Debug.Log in tests — Assert only

References

Via read_skill_file("unity-test-unit", "references/<file>"):

• test-patterns.md — data-focused patterns, NSubstitute mocking
• unity-test-attributes.md — [Test], [UnityTest], Edit vs Play mode

Via read_skill_file("unity-standards", "references/test/<file>"):

• edit-mode-patterns.md · play-mode-patterns.md · naming-conventions.md · coverage-strategy.md