diff --git a/pkg/observability/buffer.go b/pkg/observability/buffer.go
index 07b63de..791165a 100644
--- a/pkg/observability/buffer.go
+++ b/pkg/observability/buffer.go
@@ -14,7 +14,7 @@ func (o *Observability) WriteBufferToStorage(n int64) error {
 	o.ActiveBufferWriters.Add(1)
 	defer o.ActiveBufferWriters.Done()
 	// copy first to temporary buffer (storage might have latency)
-	tempBuf := bytes.NewBuffer(make([]byte, n))
+	tempBuf := bytes.NewBuffer(make([]byte, 0, n))
 	_, err := io.CopyN(tempBuf, o.Buffer, n)
 	o.LastFlushed = time.Now()
 	if err != nil && err != io.EOF {
diff --git a/pkg/observability/handlers_test.go b/pkg/observability/handlers_test.go
index 880a883..006cb5c 100644
--- a/pkg/observability/handlers_test.go
+++ b/pkg/observability/handlers_test.go
@@ -12,9 +12,8 @@ import (
 
 func TestIngestionHandler(t *testing.T) {
 	storage := &memorystorage.MockMemoryStorage{}
-	o := &Observability{
-		Storage: storage,
-	}
+	o := NewWithoutMonitor(20)
+	o.Storage = storage
 	payload := IncomingData{
 		{
 			"date": 1720613813.197045,
@@ -35,10 +34,17 @@ func TestIngestionHandler(t *testing.T) {
 		t.Fatalf("expected status code OK. Got: %d", res.StatusCode)
 	}
 
-	err = o.WriteBufferToStorage(int64(o.Buffer.Len()))
-	if err != nil {
-		t.Fatalf("write buffer to storage error: %s", err)
+	// wait until all data is flushed
+	o.ActiveBufferWriters.Wait()
+
+	// flush remaining data that hasn't been flushed
+	if n := o.Buffer.Len(); n >= 0 {
+		err := o.WriteBufferToStorage(int64(n))
+		if err != nil {
+			t.Fatalf("write log buffer to storage error (buffer: %d): %s", o.Buffer.Len(), err)
+		}
 	}
+
 	dirlist, err := storage.ReadDir("")
 	if err != nil {
 		t.Fatalf("read dir error: %s", err)
@@ -52,7 +58,7 @@ func TestIngestionHandler(t *testing.T) {
 	}
 	decodedMessages := decodeMessage(messages)
 	if decodedMessages[0].Date != 1720613813.197045 {
-		t.Fatalf("unexpected date")
+		t.Fatalf("unexpected date. Got %f, expected: %f", decodedMessages[0].Date, 1720613813.197045)
 	}
 	if decodedMessages[0].Data["log"] != "this is a string" {
 		t.Fatalf("unexpected log data")