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thomhurst merged 4 commits into from
Mar 26, 2026
Merged

feat: add test discovery Activity span for tracing #5246

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2142472
feat: add test discovery Activity span for OpenTelemetry tracing
thomhurst Mar 25, 2026
2f239c5
fix: address Claude's review - parameter ordering, catch pattern, and…
Copilot Mar 26, 2026
329668b
docs: expand OpenTelemetry setup with raw ActivityListener example an…
Copilot Mar 26, 2026
fd4914b
docs: use [Before(TestDiscovery)] for trace listener registration
Copilot Mar 26, 2026
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174 changes: 92 additions & 82 deletions TUnit.Engine/TestDiscoveryService.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,61 +60,7 @@ public async Task<TestDiscoveryResult> DiscoverTests(string testSessionId, ITest
var contextProvider = _testExecutor.GetContextProvider();
contextProvider.BeforeTestDiscoveryContext.RestoreExecutionContext();

var allTests = new List<AbstractExecutableTest>();

#pragma warning disable TPEXP
var isNopFilter = filter is NopFilter;
#pragma warning restore TPEXP
if (filter == null || !isForExecution || isNopFilter)
{
var buildingContext = new Building.TestBuildingContext(isForExecution, Filter: null);
await foreach (var test in DiscoverTestsStreamAsync(testSessionId, buildingContext, cancellationToken).ConfigureAwait(false))
{
allTests.Add(test);
}
}
else
{
// Use filter-aware collection to pre-filter by type before materializing all metadata
var allMetadata = await _testBuilderPipeline.CollectTestMetadataAsync(testSessionId, filter).ConfigureAwait(false);
var allMetadataList = allMetadata.ToList();

var metadataToInclude = _dependencyExpander.ExpandToIncludeDependencies(allMetadataList, filter);

// Build tests directly from the pre-collected metadata (avoid re-collecting)
// Apply 5-minute discovery timeout matching the streaming path (#4715)
using var filterCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
filterCts.CancelAfter(EngineDefaults.DiscoveryTimeout);

var buildingContext = new Building.TestBuildingContext(isForExecution, Filter: null);
var tests = await _testBuilderPipeline.BuildTestsFromMetadataAsync(
metadataToInclude,
buildingContext,
filterCts.Token).ConfigureAwait(false);

var testsList = tests.ToList();

// Cache tests so ITestFinder can locate them
foreach (var test in testsList)
{
_cachedTests.Add(test);
}

allTests.AddRange(testsList);
}

foreach (var test in allTests)
{
_dependencyResolver.RegisterTest(test);
}

// Resolve dependencies in parallel — registration is complete so lookup dictionaries
// are effectively read-only, and each test's Dependencies are written independently.
_dependencyResolver.BatchResolveDependencies(allTests);

// Populate TestContext._dependencies for ALL tests before After(TestDiscovery) hooks run.
// This ensures hooks can access dependency information on any TestContext (including focused tests).
_testBuilderPipeline.PopulateAllDependencies(allTests);
var allTests = await DiscoverAndResolveTestsAsync(testSessionId, filter, isForExecution, cancellationToken).ConfigureAwait(false);

// Add tests to context and run After(TestDiscovery) hooks before event receivers
// This marks the end of the discovery phase, before registration begins
Expand Down Expand Up @@ -155,6 +101,94 @@ public async Task<TestDiscoveryResult> DiscoverTests(string testSessionId, ITest
return new TestDiscoveryResult(filteredTests, finalContext);
}

private async Task<List<AbstractExecutableTest>> DiscoverAndResolveTestsAsync(
string testSessionId,
ITestExecutionFilter? filter,
bool isForExecution,
CancellationToken cancellationToken)
{
#if NET
Activity? discoveryActivity = null;
if (TUnitActivitySource.Source.HasListeners())
{
var sessionActivity = _testExecutor.GetContextProvider().TestSessionContext.Activity;
discoveryActivity = TUnitActivitySource.StartActivity(
"test discovery",
ActivityKind.Internal,
sessionActivity?.Context ?? default);
}
#endif

var allTests = new List<AbstractExecutableTest>();

try
{
#pragma warning disable TPEXP
var isNopFilter = filter is NopFilter;
#pragma warning restore TPEXP
if (filter == null || !isForExecution || isNopFilter)
{
var buildingContext = new Building.TestBuildingContext(isForExecution, Filter: null);
await foreach (var test in DiscoverTestsStreamAsync(testSessionId, buildingContext, cancellationToken).ConfigureAwait(false))
{
allTests.Add(test);
}
}
else
{
// Use filter-aware collection to pre-filter by type before materializing all metadata
var allMetadata = await _testBuilderPipeline.CollectTestMetadataAsync(testSessionId, filter).ConfigureAwait(false);
var allMetadataList = allMetadata.ToList();

var metadataToInclude = _dependencyExpander.ExpandToIncludeDependencies(allMetadataList, filter);

// Apply 5-minute discovery timeout matching the streaming path (#4715)
using var filterCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
filterCts.CancelAfter(EngineDefaults.DiscoveryTimeout);

var buildingContext = new Building.TestBuildingContext(isForExecution, Filter: null);
var tests = await _testBuilderPipeline.BuildTestsFromMetadataAsync(
metadataToInclude,
buildingContext,
filterCts.Token).ConfigureAwait(false);

var testsList = tests.ToList();

foreach (var test in testsList)
{
_cachedTests.Add(test);
_dependencyResolver.RegisterTest(test);
}

allTests.AddRange(testsList);
}

_dependencyResolver.BatchResolveDependencies(allTests);
_testBuilderPipeline.PopulateAllDependencies(allTests);

return allTests;
}
#if NET
catch (Exception ex)
{
TUnitActivitySource.RecordException(discoveryActivity, ex);
throw;
}
#else
catch
{
throw;
}
#endif
finally
{
#if NET
discoveryActivity?.SetTag("tunit.test.count", allTests.Count);
TUnitActivitySource.StopActivity(discoveryActivity);
#endif
}
}

private async IAsyncEnumerable<AbstractExecutableTest> DiscoverTestsStreamAsync(
string testSessionId,
Building.TestBuildingContext buildingContext,
Expand Down Expand Up @@ -183,25 +217,13 @@ public async IAsyncEnumerable<AbstractExecutableTest> DiscoverTestsFullyStreamin
{
await _testExecutor.ExecuteBeforeTestDiscoveryHooksAsync(cancellationToken).ConfigureAwait(false);

var buildingContext = new Building.TestBuildingContext(IsForExecution: false, Filter: null);

var allTests = new List<AbstractExecutableTest>();
await foreach (var test in DiscoverTestsStreamAsync(testSessionId, buildingContext, cancellationToken).ConfigureAwait(false))
{
allTests.Add(test);
}

// Resolve dependencies in parallel — registration is complete so lookup dictionaries
// are effectively read-only, and each test's Dependencies are written independently.
_dependencyResolver.BatchResolveDependencies(allTests);
var contextProvider = _testExecutor.GetContextProvider();

// Populate TestContext._dependencies for ALL tests before After(TestDiscovery) hooks run.
// This ensures hooks can access dependency information on any TestContext (including focused tests).
_testBuilderPipeline.PopulateAllDependencies(allTests);
var allTests = await DiscoverAndResolveTestsAsync(
testSessionId, filter: null, isForExecution: false, cancellationToken).ConfigureAwait(false);

// Add tests to context and run After(TestDiscovery) hooks before event receivers
// This marks the end of the discovery phase, before registration begins
var contextProvider = _testExecutor.GetContextProvider();
contextProvider.TestDiscoveryContext.AddTests(allTests.Select(static t => t.Context));
await _testExecutor.ExecuteAfterTestDiscoveryHooksAsync(cancellationToken).ConfigureAwait(false);
contextProvider.TestDiscoveryContext.RestoreExecutionContext();
Expand Down Expand Up @@ -274,18 +296,6 @@ public async IAsyncEnumerable<AbstractExecutableTest> DiscoverTestsFullyStreamin
}
}

private bool AreAllDependenciesSatisfied(AbstractExecutableTest test, ConcurrentDictionary<string, bool> completedTests)
{
foreach (var dependency in test.Dependencies)
{
if (!completedTests.ContainsKey(dependency.Test.TestId))
{
return false;
}
}
return true;
}



private async Task InvokePostResolutionEventsInParallelAsync(List<AbstractExecutableTest> allTests)
Expand Down
71 changes: 64 additions & 7 deletions docs/docs/examples/opentelemetry.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,14 +8,16 @@ Activity tracing requires .NET 8 or later. It is not available on .NET Framework

## Setup

### Option A: OpenTelemetry SDK (recommended)

Add the OpenTelemetry packages to your test project:

```bash
dotnet add package OpenTelemetry
dotnet add package OpenTelemetry.Exporter.Console
```

Then subscribe to the `"TUnit"` ActivitySource in your test setup:
Then subscribe to the `"TUnit"` ActivitySource in a `[Before(TestDiscovery)]` hook:

```csharp
using System.Diagnostics;
Expand All @@ -27,7 +29,7 @@ public class TraceSetup
{
private static TracerProvider? _tracerProvider;

[Before(TestSession)]
[Before(TestDiscovery)]
public static void SetupTracing()
{
_tracerProvider = Sdk.CreateTracerProviderBuilder()
Expand All @@ -47,17 +49,64 @@ public class TraceSetup

Replace `AddConsoleExporter()` with your preferred exporter (Jaeger, Zipkin, OTLP, etc.).

### Option B: Raw `ActivityListener` (no SDK dependency)

If you don't want the OpenTelemetry SDK, you can subscribe directly with a `System.Diagnostics.ActivityListener`:

```csharp
using System.Diagnostics;

public class TraceSetup
{
private static ActivityListener? _listener;

[Before(TestDiscovery)]
public static void SetupTracing()
{
_listener = new ActivityListener
{
ShouldListenTo = source => source.Name == "TUnit",
Sample = (ref ActivityCreationOptions<ActivityContext> _) => ActivitySamplingResult.AllDataAndRecorded,
ActivityStarted = activity => Console.WriteLine($"▶ {activity.OperationName}"),
ActivityStopped = activity => Console.WriteLine($"■ {activity.OperationName} ({activity.Duration.TotalMilliseconds:F1}ms)")
};
ActivitySource.AddActivityListener(_listener);
}

[After(TestSession)]
public static void TeardownTracing()
{
_listener?.Dispose();
}
}
```

### Why `[Before(TestDiscovery)]`?

The listener **must** be registered in a `[Before(TestDiscovery)]` hook (or earlier, e.g. `[Before(TestSession)]`) so it is active before the discovery span begins. TUnit's hook execution order is:

1. `[Before(TestSession)]` — session-level setup
2. `[Before(TestDiscovery)]` — register your listener here
3. **Test discovery** — the `"test discovery"` span is emitted here
4. Test execution — assembly, suite, and test case spans are emitted
5. `[After(TestSession)]` — dispose your listener here

If you register the listener later (e.g., in `[Before(Assembly)]`), the discovery span will not be captured.

## Span Hierarchy

TUnit creates a nested span tree that mirrors the test lifecycle:

```
test session
├── test discovery
└── test assembly
└── test suite (one per test class)
└── test case (one per test method invocation)
```

The **test discovery** span captures the time spent finding, building, and resolving dependencies for all tests. It appears as a sibling of the assembly spans, giving you a clear view of discovery vs execution time.

## Attributes

Each span carries tags that follow [OpenTelemetry semantic conventions](https://opentelemetry.io/docs/specs/semconv/) where applicable.
Expand Down Expand Up @@ -86,7 +135,7 @@ Each span carries tags that follow [OpenTelemetry semantic conventions](https://
| `tunit.test.method` | test case | Method name |
| `tunit.test.id` | test case | Unique test instance ID |
| `tunit.test.categories` | test case | Test categories (string array) |
| `tunit.test.count` | session/assembly/suite | Total test count |
| `tunit.test.count` | session/assembly/suite/discovery | Total test count |
| `tunit.test.retry_attempt` | test case | Current retry attempt (when retrying) |
| `tunit.test.skip_reason` | test case | Reason the test was skipped |

Expand All @@ -104,17 +153,25 @@ When a test is configured with `[Retry]`, each failed attempt produces its own s

## Using with Jaeger, Zipkin, or OTLP

Swap the exporter in the setup:
Swap the exporter in the setup code above. Each exporter needs its own NuGet package.

```csharp
// OTLP (works with Jaeger, Tempo, Honeycomb, etc.)
### OTLP (works with Jaeger, Tempo, Honeycomb, etc.)

```bash
dotnet add package OpenTelemetry.Exporter.OpenTelemetryProtocol
```

```csharp
.AddOtlpExporter(opts => opts.Endpoint = new Uri("http://localhost:4317"))
```

// Zipkin
### Zipkin

```bash
dotnet add package OpenTelemetry.Exporter.Zipkin
```

```csharp
.AddZipkinExporter(opts => opts.Endpoint = new Uri("http://localhost:9411/api/v2/spans"))
```

Expand Down
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