unity-test-framework

Overview

Disambiguation up front. This skill covers the Unity game-engine Test Framework - the official Unity package com.unity.test-framework documented at docs.unity3d.com/Packages/com.unity.test-framework@latest (opens in new window). It is distinct from the ThrowTheSwitch Unity C testing library at throwtheswitch.org/unity (opens in new window) (a single-C-file unit-test framework for bare-metal MCUs). The two tools share only a name; they have unrelated origins, APIs, and consumers. For the C unit-test library, see the sibling skill unity-test-framework-c in the qa-embedded plugin.

UTF is built on NUnit 3.5 and supports both Edit Mode and Play Mode across Standalone, Android, and iOS target platforms (per the package overview (opens in new window)).

Versioning. UTF is currently v1.8; the stable doc links below pin to the v1.4 manual snapshot for durable URLs. Both describe the same package.

Composes with:

• platform-cert-overview-reference for what category of test each Unity test belongs to (functional / performance / etc.), and for cert-gated requirements UTF tests should cover (XR-001 Title Stability, XR-074 Service Loss, XR-115 Controller add / remove).
• multiplayer-state-machine-coverage and gameplay-recording-replay for state-machine and replay-driven test patterns inside UTF PlayMode tests.

When to use

• Unit under test is C# Unity code that needs the Unity runtime (MonoBehaviour, GameObject, coroutines, scenes) or editor (AssetDatabase, EditorWindow) APIs available.
• You want CI-runnable tests that integrate with Unity Cloud Build, GitHub Actions, or other CI via Unity's batch-mode CLI.
• You need both isolated logic tests (EditMode) and integration tests that exercise scene lifecycle (PlayMode) in one harness.

For C unit tests on the firmware side of a hybrid game build, use unity-test-framework-c instead.

Authoring

Install via Package Manager

UTF "is shipped with the Unity Editor and should be automatically included in any project created with Unity 2019.2 or later" (per the package overview). For manual install, open Package Manager → + → "Add package by name…" → com.unity.test-framework.

The Test Runner window is at Window → General → Test Runner (may be Window → Test Runner depending on Editor version).

EditMode tests

Per the Edit Mode vs Play Mode tests page (opens in new window), Edit Mode tests "are only run in the Unity Editor and have access to the Editor code in addition to the game code".

Layout (two options):

• Editor folder (legacy): place tests under any folder named Editor/. Unity auto-scopes them to the Editor platform.
• Assembly definition (recommended): create an .asmdef with "includePlatforms": ["Editor"].

Minimal example:

using NUnit.Framework;
using UnityEngine;

namespace MyGame.Tests.EditMode
{
    public class HealthComponentTests
    {
        [Test]
        public void Damage_DeductsCorrectAmount()
        {
            var go = new GameObject();
            var health = go.AddComponent<HealthComponent>();
            health.Initialize(maxHealth: 100);

            health.ApplyDamage(35);

            Assert.AreEqual(65, health.Current);
        }

        [TearDown]
        public void Cleanup()
        {
            // EditMode tests must clean up created GameObjects;
            // they don't auto-tear-down between cases.
        }
    }
}

The docs recommend the NUnit Test attribute rather than UnityTest unless you need to yield special instructions in Edit Mode, or skip a frame / wait for an amount of time in Play Mode.

PlayMode tests

PlayMode tests "execute as coroutines within the game runtime and can run standalone in a Player or within the Editor". Assembly definition:

{
  "name": "MyGame.Tests.PlayMode",
  "references": ["MyGame.Runtime"],
  "optionalUnityReferences": ["TestAssemblies"],
  "includePlatforms": []
}

Per the edit-mode-vs-play-mode docs, the .asmdef must reference the code under test ("references": ["NewAssembly"]), optionally include "optionalUnityReferences": ["TestAssemblies"], and leave "includePlatforms": [] empty to allow multiple target platforms.

Minimal example:

using System.Collections;
using NUnit.Framework;
using UnityEngine;
using UnityEngine.TestTools;

namespace MyGame.Tests.PlayMode
{
    public class EnemyAITests
    {
        [UnityTest]
        public IEnumerator Enemy_PursuesPlayer_WithinRange()
        {
            var player = new GameObject("Player");
            var enemy  = Object.Instantiate(Resources.Load<GameObject>("Enemy"));
            enemy.transform.position = new Vector3(10f, 0f, 0f);

            yield return new WaitForSeconds(2f);

            var distance = Vector3.Distance(player.transform.position,
                                            enemy.transform.position);
            Assert.Less(distance, 5f, "Enemy did not close on player");
        }
    }
}

The [UnityTest] attribute, returning IEnumerator, lets the test yield frames (yield return null), seconds (yield return new WaitForSeconds(2f)), or custom yield instructions - necessary for any frame-driven behaviour.

Attributes

The common attributes are [Test] (synchronous NUnit), [UnityTest] (coroutine, yields frames/seconds), [SetUp] / [TearDown], [OneTimeSetUp] / [OneTimeTearDown], [Category("Smoke")] (CLI-selectable), and [UnityPlatform(...)]. The full cheatsheet with sources and the ValueSource parameterisation note is in references/attributes.md.

NUnit assertion APIs

UTF is built on NUnit 3.5, so the full NUnit 3 assertion model applies - Assert.AreEqual, Assert.Throws<T>(() => ...), Assert.That(actual, Is.EqualTo(expected).Within(0.01f)), etc. Prefer the NUnit Test attribute over UnityTest unless you need to yield special instructions.

Running

From the Test Runner window

Window → General → Test Runner (path may be Window → Test Runner in older Editor versions). The window shows two tabs:

• EditMode - synchronous tests executed against the editor domain.
• PlayMode - tests that enter and exit play mode for each fixture.

Click Run All, Run Selected, or right-click a fixture → Run to execute. Results display inline with stack traces on failure.

From the command line (batch mode)

Invoke Unity in batch mode and treat the -testResults XML as the source of truth (Unity has no common exit-code definition):

Unity \
  -batchmode \
  -projectPath "$PWD" \
  -runTests \
  -testPlatform PlayMode \
  -testResults artifacts/playmode-results.xml \
  -testCategory "Smoke" \
  -logFile artifacts/unity.log

The full batch-mode flag table (-testFilter, -testPlatform, -assemblyNames, ordering / retry flags), the Windows invocation, and the exit-code caveat are in references/cli.md.

Parsing results

The -testResults XML is NUnit 3 result format. Surface result="Failed" at the <test-run> level for the overall verdict, then enumerate <test-case result="Failed"> for per-test detail; nunit-junit-xml converters exist for JUnit consumers. The full schema example is in references/results-and-ci.md.

CI integration

Run UTF in CI via game-ci/unity-test-runner (or the bare batch-mode CLI), upload the -testResults XML as an artifact, and cache the Library/ folder across runs - Unity re-imports all assets without it, adding 5 - 15 min per run. A complete GitHub Actions workflow is in references/results-and-ci.md.

Anti-patterns

Limitations

Known constraints (per the v1.4 manual index):

• No WSA platform support for UnityTest - Windows Store Apps cannot run [UnityTest] coroutine-style tests.
• Parameterised tests unsupported (except ValueSource) - NUnit [TestCase], [TestCaseSource] have historical caveats in UTF.
• [Repeat] attribute incompatibility - listed as a known limitation.
• Nested test fixtures cannot run from the Editor UI.
• [Retry] attribute causes InvalidCastException in PlayMode tests.

Other practical limitations:

• Asset Database in PlayMode is sandboxed. PlayMode tests cannot freely create / mutate assets the way EditMode tests can.
• Coverage requires the separate com.unity.testtools.codecoverage package; not included by default.
• License gating on CI - Unity batch-mode CI requires either an activated Personal/Plus license seat or a manual .ulf license file; consult Unity's documentation for the current activation flow before standing up CI. Keep the seat credentials or the .ulf contents in the CI secret store and inject them as environment variables; never write them into a workflow file or a logged command line.
• No public common exit-code definition (per the command-line reference); parse XML, don't rely on exit code.
• EditMode test that enters PlayMode is supported ("Edit Mode tests can control entering and exiting Play Mode from your test") but cross-mode tests are notoriously flaky; prefer keeping the two modes' tests separate.