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Merged
thomhurst merged 3 commits into from
Jan 11, 2026
Merged

perf: lazy initialization for TestBuilderContext properties #4305

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77f3e6b
docs: add lazy test materialization design plan
thomhurst Jan 11, 2026
d13c5e6
Merge branch 'main' of https://github.com/thomhurst/TUnit
thomhurst Jan 11, 2026
38e1995
perf: lazy initialization for TestBuilderContext properties
thomhurst Jan 11, 2026
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21 changes: 18 additions & 3 deletions TUnit.Core/TestBuilderContext.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ namespace TUnit.Core;
public record TestBuilderContext
{
private static readonly AsyncLocal<TestBuilderContext?> BuilderContexts = new();
private string? _definitionId;

/// <summary>
/// Gets the current test builder context.
Expand All @@ -19,17 +20,31 @@ public static TestBuilderContext? Current
internal set => BuilderContexts.Value = value;
}

public string DefinitionId { get; } = Guid.NewGuid().ToString();
/// <summary>
/// Gets the unique definition ID for this context. Generated lazily on first access.
/// </summary>
public string DefinitionId => _definitionId ??= Guid.NewGuid().ToString();

[Obsolete("Use StateBag property instead.")]
public ConcurrentDictionary<string, object?> ObjectBag => StateBag;

private ConcurrentDictionary<string, object?>? _stateBag;
private TestContextEvents? _events;

/// <summary>
/// Gets the state bag for storing arbitrary data during test building.
/// </summary>
public ConcurrentDictionary<string, object?> StateBag { get; set; } = new();
public ConcurrentDictionary<string, object?> StateBag
{
get => _stateBag ??= new ConcurrentDictionary<string, object?>();
set => _stateBag = value;
}

public TestContextEvents Events { get; set; } = new();
public TestContextEvents Events
{
get => _events ??= new TestContextEvents();
set => _events = value;
}

public IDataSourceAttribute? DataSourceAttribute { get; set; }

Expand Down
19 changes: 7 additions & 12 deletions TUnit.Engine/Building/TestBuilder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -162,11 +162,10 @@ public async Task<IEnumerable<AbstractExecutableTest>> BuildTestsFromMetadataAsy
}

// Create a single context accessor that we'll reuse, updating its Current property for each test
// StateBag and Events are lazy-initialized, so we don't need to pre-allocate them
var testBuilderContext = new TestBuilderContext
{
TestMetadata = metadata.MethodMetadata,
Events = new TestContextEvents(),
StateBag = new ConcurrentDictionary<string, object?>(),
InitializedAttributes = attributes // Store the initialized attributes
};

Expand Down Expand Up @@ -309,11 +308,10 @@ await _objectLifecycleService.RegisterObjectAsync(
for (var i = 0; i < repeatCount + 1; i++)
{
// Update context BEFORE calling data factories so they track objects in the right context
// StateBag and Events are lazy-initialized for performance
contextAccessor.Current = new TestBuilderContext
{
TestMetadata = metadata.MethodMetadata,
Events = new TestContextEvents(),
StateBag = new ConcurrentDictionary<string, object?>(),
DataSourceAttribute = methodDataSource,
InitializedAttributes = testBuilderContext.InitializedAttributes, // Preserve attributes from parent context
ClassConstructor = testBuilderContext.ClassConstructor // Preserve ClassConstructor for instance creation
Expand Down Expand Up @@ -443,10 +441,10 @@ await _objectLifecycleService.RegisterObjectAsync(
Metadata = finalMetadata
};

// Events is lazy-initialized; explicitly share StateBag from per-iteration context
var testSpecificContext = new TestBuilderContext
{
TestMetadata = metadata.MethodMetadata,
Events = new TestContextEvents(),
StateBag = contextAccessor.Current.StateBag,
ClassConstructor = testBuilderContext.ClassConstructor,
DataSourceAttribute = contextAccessor.Current.DataSourceAttribute,
Expand Down Expand Up @@ -508,11 +506,10 @@ await _objectLifecycleService.RegisterObjectAsync(
ResolvedMethodGenericArguments = Type.EmptyTypes
};

// StateBag and Events are lazy-initialized
var testSpecificContext = new TestBuilderContext
{
TestMetadata = metadata.MethodMetadata,
Events = new TestContextEvents(),
StateBag = new ConcurrentDictionary<string, object?>(),
ClassConstructor = testBuilderContext.ClassConstructor,
DataSourceAttribute = methodDataSource,
InitializedAttributes = attributes
Expand Down Expand Up @@ -568,11 +565,10 @@ await _objectLifecycleService.RegisterObjectAsync(
ResolvedMethodGenericArguments = Type.EmptyTypes
};

// StateBag and Events are lazy-initialized
var testSpecificContext = new TestBuilderContext
{
TestMetadata = metadata.MethodMetadata,
Events = new TestContextEvents(),
StateBag = new ConcurrentDictionary<string, object?>(),
ClassConstructor = testBuilderContext.ClassConstructor,
DataSourceAttribute = classDataSource,
InitializedAttributes = attributes
Expand Down Expand Up @@ -1428,11 +1424,10 @@ public async IAsyncEnumerable<AbstractExecutableTest> BuildTestsStreamingAsync(
var attributes = await InitializeAttributesAsync(metadata.AttributeFactory.Invoke());

// Create base context with ClassConstructor if present
// StateBag and Events are lazy-initialized for performance
var baseContext = new TestBuilderContext
{
TestMetadata = metadata.MethodMetadata,
Events = new TestContextEvents(),
StateBag = new ConcurrentDictionary<string, object?>(),
InitializedAttributes = attributes // Store the initialized attributes
};

Expand Down Expand Up @@ -1732,10 +1727,10 @@ private Task<InstanceCreationResult> CreateInstanceForMethodDataSources(
Metadata = finalMetadata
};

// Events is lazy-initialized; explicitly share StateBag from per-iteration context
var testSpecificContext = new TestBuilderContext
{
TestMetadata = metadata.MethodMetadata,
Events = new TestContextEvents(),
StateBag = contextAccessor.Current.StateBag,
ClassConstructor = contextAccessor.Current.ClassConstructor,
DataSourceAttribute = contextAccessor.Current.DataSourceAttribute,
Expand Down
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