[#88] netmap: fix min aggregator bug, add tests

Signed-off-by: Andrew Danilin <andnilin@gmail.com>

netmap/aggregator.go

@@ -23,7 +23,7 @@ type (
 	}
 
 	minAgg struct {
-		min float64
+		min *float64
 	}
 
 	meanIQRAgg struct {
@@ -102,13 +102,17 @@ func (a *meanAgg) Compute() float64 {
 }
 
 func (a *minAgg) Add(n float64) {
-	if a.min == 0 || n < a.min {
-		a.min = n
+	if a.min == nil || n < *a.min {
+		a.min = &n
 	}
 }
 
 func (a *minAgg) Compute() float64 {
-	return a.min
+	if a.min == nil {
+		return 0
+	}
+
+	return *a.min
 }
 
 func (a *meanIQRAgg) Add(n float64) {

netmap/aggregator_test.go

@@ -0,0 +1,44 @@
+package netmap
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestMinAgg(t *testing.T) {
+	tests := []struct {
+		vals []float64
+		res  float64
+	}{
+		{
+			vals: []float64{1, 2, 3, 0, 10},
+			res:  0,
+		},
+		{
+			vals: []float64{10, 0, 10, 0},
+			res:  0,
+		},
+		{
+			vals: []float64{0, 1, 2, 3, 10},
+			res:  0,
+		},
+		{
+			vals: []float64{0, 0, 0, 0},
+			res:  0,
+		},
+		{
+			vals: []float64{10, 10, 10, 10},
+			res:  10,
+		},
+	}
+
+	for _, test := range tests {
+		a := newMinAgg()
+		for _, val := range test.vals {
+			a.Add(val)
+		}
+
+		require.Equal(t, test.res, a.Compute())
+	}
+}