diff --git a/pkg/statistics/statistics.go b/pkg/statistics/statistics.go
index 0107fe7..4e8fa91 100644
--- a/pkg/statistics/statistics.go
+++ b/pkg/statistics/statistics.go
@@ -26,10 +26,7 @@ import (
 	"go.opentelemetry.io/otel/metric"
 )
 
-func key(key string) string {
-	return "dataset." + key
-}
-
+// Statistics related to data processing
 type Statistics struct {
 	buffersEnqueued  atomic.Uint64
 	buffersProcessed atomic.Uint64
@@ -63,6 +60,9 @@ type Statistics struct {
 	hResponseTime metric.Int64Histogram
 }
 
+// NewStatistics creates structure to keep track of data processing.
+// If meter is not nil, then Open Telemetry is used for collecting metrics
+// as well.
 func NewStatistics(meter *metric.Meter) (*Statistics, error) {
 	statistics := &Statistics{
 		buffersEnqueued:  atomic.Uint64{},
@@ -86,6 +86,10 @@ func NewStatistics(meter *metric.Meter) (*Statistics, error) {
 	return statistics, err
 }
 
+func key(key string) string {
+	return "dataset." + key
+}
+
 func (stats *Statistics) initMetrics(meter *metric.Meter) error {
 	// if there is no meter, there is no need to initialise counters
 	if meter == nil {
@@ -275,6 +279,7 @@ func (stats *Statistics) add(counter metric.Int64UpDownCounter, i uint64) {
 	}
 }
 
+// Export exports statistics related to the processing
 func (stats *Statistics) Export(processingDur time.Duration) *ExportedStatistics {
 	// log buffer stats
 	bProcessed := stats.buffersProcessed.Load()
diff --git a/pkg/statistics/statistics_test.go b/pkg/statistics/statistics_test.go
index b0f772b..91c6b41 100644
--- a/pkg/statistics/statistics_test.go
+++ b/pkg/statistics/statistics_test.go
@@ -209,4 +209,40 @@ func TestExport(t *testing.T) {
 			processingTime:   time.Second,
 		},
 	}, exp)
+
+	assert.Equal(t, exp.Buffers.Enqueued(), uint64(1000))
+	assert.Equal(t, exp.Buffers.Processed(), uint64(100))
+	assert.Equal(t, exp.Buffers.Dropped(), uint64(10))
+	assert.Equal(t, exp.Buffers.Broken(), uint64(1))
+	assert.Equal(t, exp.Buffers.Waiting(), uint64(889))
+	assert.Equal(t, exp.Buffers.ProcessingTime(), time.Second)
+	assert.Equal(t, exp.Buffers.SuccessRate(), .89)
+
+	assert.Equal(t, exp.Events.Enqueued(), uint64(2000))
+	assert.Equal(t, exp.Events.Processed(), uint64(200))
+	assert.Equal(t, exp.Events.Dropped(), uint64(20))
+	assert.Equal(t, exp.Events.Broken(), uint64(2))
+	assert.Equal(t, exp.Events.Waiting(), uint64(1778))
+	assert.Equal(t, exp.Events.ProcessingTime(), time.Second)
+	assert.Equal(t, exp.Events.SuccessRate(), .89)
+
+	assert.Equal(t, exp.Transfer.BytesSent(), uint64(3000))
+	assert.Equal(t, exp.Transfer.BytesAccepted(), uint64(300))
+	assert.Equal(t, exp.Transfer.BuffersProcessed(), uint64(100))
+	assert.Equal(t, exp.Transfer.SuccessRate(), float64(0.1))
+	assert.Equal(t, exp.Transfer.ThroughputBpS(), float64(300))
+	assert.Equal(t, exp.Transfer.AvgBufferBytes(), float64(3))
+	assert.Equal(t, exp.Transfer.ProcessingTime(), time.Second)
+}
+
+func TestExportNoTraffic(t *testing.T) {
+	stats, err := NewStatistics(nil)
+	require.Nil(t, err)
+
+	exp := stats.Export(time.Second)
+	assert.Equal(t, exp.Events.SuccessRate(), float64(0))
+	assert.Equal(t, exp.Buffers.SuccessRate(), float64(0))
+	assert.Equal(t, exp.Transfer.SuccessRate(), float64(0))
+	assert.Equal(t, exp.Transfer.ThroughputBpS(), float64(0))
+	assert.Equal(t, exp.Transfer.AvgBufferBytes(), float64(0))
 }