Ue Automation And Testing

Automation & testing

Unreal has a layered test ecosystem. Each layer trades world setup cost against richness:

When to use this skill

• Writing C++ unit or integration tests for game systems (damage, inventory, save data).
• Expressing multi-case behavior specs that should read like documentation.
• Testing gameplay mechanics that require actors, physics, or a running world.
• Running tests headless in CI on every commit.
• Reaching devices or larger sessions via Gauntlet.

Mental model

Tests live outside UObject reflection — they are not Blueprints-visible. The FAutomationTestBase base class provides the assertion API (TestTrue, TestEqual, …) and is instantiated once as a global at startup. RunTest must return true; use the assertion methods rather than check/ensure so failures record cleanly instead of crashing.

EAutomationTestFlags controls two orthogonal dimensions: context (where the test can run: EditorContext, ClientContext, ServerContext, CommandletContext, ProgramContext) and filter (which CI bucket: SmokeFilter, EngineFilter, ProductFilter, PerfFilter, StressFilter). Every test must specify at least one context and one filter.

Simple automation test

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// Private/Tests/DamageTest.cpp
#include "Misc/AutomationTest.h"

IMPLEMENT_SIMPLE_AUTOMATION_TEST(FDamageMathTest, "MyGame.Combat.DamageMath",
    EAutomationTestFlags::EditorContext | EAutomationTestFlags::EngineFilter)

bool FDamageMathTest::RunTest(const FString& Parameters)
{
    const float Result = ComputeDamage(100.f, 0.5f);
    TestEqual(TEXT("Half damage"), Result, 50.f);
    TestTrue(TEXT("Non-negative"), Result >= 0.f);
    return true;   // returning false also marks the test failed
}

Key rules:

• Place tests in Private/Tests/ of the relevant module; name the file <ClassFilename>Test.cpp.
• The dotted path string ("MyGame.Combat.DamageMath") is what the browser and command-line filter use.
• Always combine a context flag and a filter flag with |.
• Add "AutomationController" and "AutomationUtils" to PrivateDependencyModuleNames in your Build.cs if you need automation utilities.

Complex automation test

Complex tests run the same RunTest body over a set of inputs provided by GetTests. Use them for content stress (load all maps, compile all Blueprints):

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IMPLEMENT_COMPLEX_AUTOMATION_TEST(FLoadAllMapsTest, "MyGame.Maps.LoadAll",
    EAutomationTestFlags::EditorContext | EAutomationTestFlags::ProductFilter)

void FLoadAllMapsTest::GetTests(TArray<FString>& OutBeautifiedNames,
                                TArray<FString>& OutTestCommands) const
{
    // populate OutBeautifiedNames and OutTestCommands in parallel
}

bool FLoadAllMapsTest::RunTest(const FString& Parameters)
{
    // Parameters is one entry from OutTestCommands
    return true;
}

Spec style (BDD)

Specs express behavior in Describe/It blocks with scoped BeforeEach/AfterEach setup. Each It becomes an independently runnable test. Use BEGIN_DEFINE_SPEC to add member variables; DEFINE_SPEC when the class body can stay empty.

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BEGIN_DEFINE_SPEC(FInventorySpec, "MyGame.Inventory",
    EAutomationTestFlags::EditorContext | EAutomationTestFlags::ProductFilter)
    TSharedPtr<FInventorySystem> Inv;
END_DEFINE_SPEC(FInventorySpec)

void FInventorySpec::Define()
{
    BeforeEach([this]()
    {
        Inv = MakeShared<FInventorySystem>();
    });

    Describe("AddItem", [this]()
    {
        It("should increase count by one", [this]()
        {
            Inv->AddItem(TEXT("Sword"), 1);
            TestEqual(TEXT("Count"), Inv->GetCount(TEXT("Sword")), 1);
        });

        It("should reject a stack over the limit", [this]()
        {
            TestFalse(TEXT("Over limit"),
                Inv->AddItem(TEXT("Arrows"), 9999));
        });
    });

    AfterEach([this]() { Inv.Reset(); });
}

• Name spec files <FeatureName>.spec.cpp — not *Test.cpp.
• xDescribe / xIt disable a block without deleting it.
• Use LatentIt / LatentBeforeEach when a test step spans multiple frames (passes a FDoneDelegate).
• Pass EAsyncExecution::TaskGraph / ::ThreadPool to It / BeforeEach to control which thread each block runs on.

See references/spec-and-latent-commands.md for BeforeEach scoping, parameterized tests, async/latent patterns, and Redefine.

Functional tests (in a level)

AFunctionalTest is a UCLASS actor placed in a dedicated test map. The automation runner discovers it through the Functional Testing Editor plugin, starts each actor, and collects results.

Override the key virtual functions in a C++ child class:

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// MyFunctionalTest.h
UCLASS()
class MYGAME_API AMyFunctionalTest : public AFunctionalTest
{
    GENERATED_BODY()
protected:
    virtual void PrepareTest() override;      // start async setup (streaming, server)
    virtual bool IsReady_Implementation();    // return false while still loading
    virtual void StartTest();                 // main test body
};

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// MyFunctionalTest.cpp — inside StartTest:
void AMyFunctionalTest::StartTest()
{
    AMyActor* Target = Cast<AMyActor>(FindActorByTag(TEXT("Target")));
    AssertIsValid(Target, TEXT("Target actor found"));
    AssertTrue(Target->Health > 0.f, TEXT("Target is alive"));
    FinishTest(EFunctionalTestResult::Succeeded, TEXT("OK"));
}

Important:

• FinishTest must be called or the test times out. Set TimeLimit in the actor's details to bound CI runs.
• Use AssertTrue / AssertIsValid / AssertEqual_Float (the functional-test assert family from AFunctionalTest) rather than the FAutomationTestBase macros.
• Register spawned actors with AddActorToDestroyOnTestEnd so cleanup is automatic.

See references/functional-tests.md for PrepareTest and IsReady patterns, Ground Truth Data, and Blueprint functional test setup.

Low-level tests (Catch2 / LLT)

LLTs compile a separate thin executable per module using Catch2 — no editor, no game framework — giving the fastest possible CI iteration for module-internal logic. They live in a Tests/ directory alongside the module and require a dedicated <Module>Tests.Target.cs build target. See the official doc and Developer/LowLevelTestsRunner/ for the runner harness.

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#include "TestHarness.h"   // Developer/LowLevelTestsRunner/Public/TestHarness.h

TEST_CASE("MyModule / FormatFString / basic substitution", "[smoke]")
{
    FString Out = FString::Printf(TEXT("v=%d"), 42);
    CHECK(Out == TEXT("v=42"));
}

LLTs are the right choice when your logic has no UObject or world dependency and you want sub-second CI feedback. See references/low-level-tests.md for target setup and build invocation.

Assertion reference

FAutomationTestBase assertions (all record failures without stopping execution unless you return false or call UE_RETURN_ON_ERROR):

Running tests

Editor: Tools → Test Automation → Automation tab → select tests → Start Tests.

Command line / CI (headless):

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UnrealEditor-Cmd.exe MyProject.uproject
  -ExecCmds="Automation RunTest MyGame.Combat;Quit"
  -unattended -nopause -nullrhi
  -ReportExportPath="TestResults/"

Flags:

• -ExecCmds="Automation RunTest <filter>" — dotted prefix runs all tests under it.
• -ExecCmds="Automation RunTest Group:MyGroup;Quit" — named test group (configured via AutomationTestGroup in DefaultEngine.ini).
• -ReportExportPath — writes JSON + HTML for a report server.
• -ResumeRunTest — resume an interrupted run from a saved JSON report.

Parse the exit code and log for pass/fail in your CI pipeline. A non-zero exit code indicates test failures when -unattended is set.

Gotchas

• Missing both a context and a filter flag → the test never appears in the browser.
• Using check/ensure instead of TestTrue/AddError → crashes the whole run instead of recording a failure.
• Functional test with no timeout → CI hangs indefinitely.
• Non-deterministic tests (frame timing, RNG, network) → flaky; seed or mock inputs.
• Spec variable capture inside Describe — local variables captured by lambda go out of scope before the It runs; capture this and use member variables.
• Test module depends on the editor — tests that need WITH_EDITOR types must be placed in an Editor-category module; don't put them in Runtime.
• AddErrorS / AddWarningS — deprecated since 5.4; use AddError / AddWarning.
• TestEqualInsensitive — deprecated since 5.5; use TestEqual (strings are case-insensitive by default now).

Version notes

• EAutomationTestFlags_ApplicationContextMask is a convenience constant combining all context flags; commonly used in specs: EAutomationTestFlags::ProductFilter | EAutomationTestFlags_ApplicationContextMask.
• Priority flags (CriticalPriority, HighPriority, etc.) were added in UE5; they are optional but useful for CI triage.
• Low-level tests (Catch2-based LLTs) are the recommended direction for new pure-logic tests added since UE 5.0. The FAutomationTestBase stack remains the right choice for tests that need the engine or editor context.

References & source material

Engine source (UE 5.8):

• Runtime/Core/Public/Misc/AutomationTest.h — EAutomationTestFlags:88, FAutomationTestBase:1594, RunTest:2653, TestEqual:1985, TestFalse:2367, TestNull:2530, TestTrue:2603, FAutomationSpecBase:2899, Describe:2757, BeforeEach:2821, It:2789, IAutomationLatentCommand:525, DEFINE_LATENT_AUTOMATION_COMMAND:3796, ADD_LATENT_AUTOMATION_COMMAND:4087, IMPLEMENT_SIMPLE_AUTOMATION_TEST:4297, DEFINE_SPEC:4339, BEGIN_DEFINE_SPEC:4346.
• Developer/FunctionalTesting/Classes/FunctionalTest.h — AFunctionalTest:249, FinishTest:678, PrepareTest:777, IsReady_Implementation:814, AddError:659.
• Developer/LowLevelTestsRunner/Public/TestHarness.h — Catch2 bridge/harness header.
• Developer/CQTest/ — CQTest module (TEST, TEST_CLASS, ASSERT_THAT macros).

Official docs (UE 5.8):

• Automation Test Framework — https://dev.epicgames.com/documentation/unreal-engine/automation-test-framework-in-unreal-engine
• Write C++ Tests — https://dev.epicgames.com/documentation/unreal-engine/write-cplusplus-tests-in-unreal-engine
• Automation Spec — https://dev.epicgames.com/documentation/unreal-engine/automation-spec-in-unreal-engine
• Functional Testing — https://dev.epicgames.com/documentation/unreal-engine/functional-testing-in-unreal-engine
• Run Automation Tests — https://dev.epicgames.com/documentation/unreal-engine/run-automation-tests-in-unreal-engine
• Low-Level Tests — https://dev.epicgames.com/documentation/unreal-engine/low-level-tests-in-unreal-engine
• Gauntlet Automation Framework — https://dev.epicgames.com/documentation/unreal-engine/gauntlet-automation-framework-in-unreal-engine
• CQTest — https://dev.epicgames.com/documentation/unreal-engine/cqtest-test-framework-for-unreal-engine

Deep-dive references in this skill:

• references/spec-and-latent-commands.md — Spec scoping, parameterized tests, latent/async patterns, Redefine.
• references/functional-tests.md — AFunctionalTest lifecycle, Ground Truth Data, Blueprint setup.
• references/low-level-tests.md — Catch2/LLT target setup, build invocation, CQTest.
• references/flags-and-ci.md — EAutomationTestFlags reference table, CI command patterns, report server, Gauntlet overview.

Related skills: ue-logging-and-assertions, ue-debugging-techniques.