tsdb/record: add test for clear() on histograms

tsdb/record/buffers_test.go

@@ -0,0 +1,35 @@
+package record
+
+import (
+	"testing"
+	"github.com/prometheus/prometheus/model/histogram"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBuffersPool_PtrClear(t *testing.T) {
+	pool := NewBuffersPool()
+	
+	h := pool.GetHistograms(1)
+	h = append(h, RefHistogramSample{
+		H: &histogram.Histogram{},
+	})
+	pool.PutHistograms(h)
+
+	h2 := pool.GetHistograms(1)
+	require.Len(t, h2, 0)
+	require.Equal(t, 1, cap(h2))
+	h2 = h2[:1] // extend to capacity to check previously stored item
+	require.Nil(t, h2[0].H)
+	
+	fh := pool.GetFloatHistograms(1)
+	fh = append(fh, RefFloatHistogramSample{
+		FH: &histogram.FloatHistogram{},
+	})
+	pool.PutFloatHistograms(fh)
+
+	fh2 := pool.GetFloatHistograms(1)
+	require.Len(t, fh2, 0)
+	require.Equal(t, 1, cap(fh2))
+	fh2 = fh2[:1] // extend to capacity
+	require.Nil(t, fh2[0].FH)
+}