feat(trace): add concurrent-safe Reset method to SpanRecorder (#5994)

Add Reset method to reuse it for testing. Just like in InMemoryExporter.

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Added
+
+- Add `Reset` method to `SpanRecorder` in `go.opentelemetry.io/otel/sdk/trace/tracetest`. (#5994)
+
 ### Changed
 
 - The default global API now supports full auto-instrumentation from the `go.opentelemetry.io/auto` package.

sdk/trace/tracetest/recorder.go

@@ -69,6 +69,19 @@ func (sr *SpanRecorder) Started() []sdktrace.ReadWriteSpan {
 	return dst
 }
 
+// Reset clears the recorded spans.
+//
+// This method is safe to be called concurrently.
+func (sr *SpanRecorder) Reset() {
+	sr.startedMu.Lock()
+	sr.endedMu.Lock()
+	defer sr.startedMu.Unlock()
+	defer sr.endedMu.Unlock()
+
+	sr.started = nil
+	sr.ended = nil
+}
+
 // Ended returns a copy of all ended spans that have been recorded.
 //
 // This method is safe to be called concurrently.

sdk/trace/tracetest/recorder_test.go

@@ -112,3 +112,27 @@ func TestStartingConcurrentSafe(t *testing.T) {
 
 	assert.Len(t, sr.Started(), 2)
 }
+
+func TestResetConcurrentSafe(t *testing.T) {
+	sr := NewSpanRecorder()
+	ctx := context.Background()
+
+	runConcurrently(
+		func() { sr.OnStart(ctx, new(rwSpan)) },
+		func() { sr.OnStart(ctx, new(rwSpan)) },
+		func() { sr.OnEnd(new(roSpan)) },
+		func() { sr.OnEnd(new(roSpan)) },
+	)
+
+	assert.Len(t, sr.Started(), 2)
+	assert.Len(t, sr.Ended(), 2)
+
+	runConcurrently(
+		func() { sr.Reset() },
+		func() { sr.Reset() },
+		func() { sr.Reset() },
+	)
+
+	assert.Empty(t, sr.Started())
+	assert.Empty(t, sr.Ended())
+}