Add Noop and InMemory SpanBatcher, help with testing integrations (#994)

* Add Noop and InMemory SpanBatcher, help with testing integrations

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

* Update sdk/export/trace/tracetest/test.go

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

* More feedback

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

sdk/export/trace/tracetest/test.go

@@ -0,0 +1,87 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// tracetest is a testing helper package for the SDK. User can configure no-op or in-memory exporters to verify
+// different SDK behaviors or custom instrumentation.
+package tracetest // import "go.opentelemetry.io/otel/sdk/export/trace/tracetest"
+
+import (
+	"context"
+	"sync"
+
+	"go.opentelemetry.io/otel/sdk/export/trace"
+)
+
+var _ trace.SpanBatcher = (*NoopExporter)(nil)
+var _ trace.SpanSyncer = (*NoopExporter)(nil)
+
+// NewNoopExporter returns a new no-op exporter.
+// It implements both trace.SpanBatcher and trace.SpanSyncer.
+func NewNoopExporter() *NoopExporter {
+	return new(NoopExporter)
+}
+
+// NoopExporter is an exporter that does nothing.
+type NoopExporter struct{}
+
+// ExportSpans implements the trace.SpanBatcher interface.
+func (nsb *NoopExporter) ExportSpans(context.Context, []*trace.SpanData) {}
+
+// ExportSpan implements the trace.SpanSyncer interface.
+func (nsb *NoopExporter) ExportSpan(context.Context, *trace.SpanData) {}
+
+var _ trace.SpanBatcher = (*InMemoryExporter)(nil)
+var _ trace.SpanSyncer = (*InMemoryExporter)(nil)
+
+// NewInMemoryExporter returns a new trace.SpanBatcher that stores in-memory all exported spans.
+// It implements both trace.SpanBatcher and trace.SpanSyncer.
+func NewInMemoryExporter() *InMemoryExporter {
+	return new(InMemoryExporter)
+}
+
+// InMemoryExporter is an exporter that stores in-memory all exported spans.
+type InMemoryExporter struct {
+	mu  sync.Mutex
+	sds []*trace.SpanData
+}
+
+// ExportSpans implements the trace.SpanBatcher interface.
+func (imsb *InMemoryExporter) ExportSpans(_ context.Context, sds []*trace.SpanData) {
+	imsb.mu.Lock()
+	defer imsb.mu.Unlock()
+	imsb.sds = append(imsb.sds, sds...)
+}
+
+// ExportSpan implements the trace.SpanSyncer interface.
+func (imsb *InMemoryExporter) ExportSpan(_ context.Context, sd *trace.SpanData) {
+	imsb.mu.Lock()
+	defer imsb.mu.Unlock()
+	imsb.sds = append(imsb.sds, sd)
+}
+
+// Reset the current in-memory storage.
+func (imsb *InMemoryExporter) Reset() {
+	imsb.mu.Lock()
+	defer imsb.mu.Unlock()
+	imsb.sds = nil
+}
+
+// GetSpans returns the current in-memory stored spans.
+func (imsb *InMemoryExporter) GetSpans() []*trace.SpanData {
+	imsb.mu.Lock()
+	defer imsb.mu.Unlock()
+	ret := make([]*trace.SpanData, len(imsb.sds))
+	copy(ret, imsb.sds)
+	return ret
+}

sdk/export/trace/tracetest/test_test.go

@@ -0,0 +1,61 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tracetest
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"go.opentelemetry.io/otel/sdk/export/trace"
+)
+
+// TestNoop tests only that the no-op does not crash in different scenarios.
+func TestNoop(t *testing.T) {
+	nsb := NewNoopExporter()
+
+	nsb.ExportSpans(context.Background(), nil)
+	nsb.ExportSpans(context.Background(), make([]*trace.SpanData, 10))
+	nsb.ExportSpans(context.Background(), make([]*trace.SpanData, 0, 10))
+	nsb.ExportSpan(context.Background(), nil)
+}
+
+func TestNewInMemoryExporter(t *testing.T) {
+	imsb := NewInMemoryExporter()
+
+	imsb.ExportSpans(context.Background(), nil)
+	assert.Len(t, imsb.GetSpans(), 0)
+
+	input := make([]*trace.SpanData, 10)
+	for i := 0; i < 10; i++ {
+		input[i] = new(trace.SpanData)
+	}
+	imsb.ExportSpans(context.Background(), input)
+	sds := imsb.GetSpans()
+	assert.Len(t, sds, 10)
+	for i, sd := range sds {
+		assert.Same(t, input[i], sd)
+	}
+	imsb.Reset()
+	// Ensure that operations on the internal storage does not change the previously returned value.
+	assert.Len(t, sds, 10)
+	assert.Len(t, imsb.GetSpans(), 0)
+
+	imsb.ExportSpan(context.Background(), input[0])
+	sds = imsb.GetSpans()
+	assert.Len(t, sds, 1)
+	assert.Same(t, input[0], sds[0])
+}