Improve metrics testability

cluster-autoscaler/core/scaledown/nodeevaltracker/max_node_skip_eval_time.go

@@ -22,17 +22,23 @@ import (
 	"k8s.io/autoscaler/cluster-autoscaler/metrics"
 )
 
+type metricObserver interface {
+	ObserveMaxNodeSkipEvalDurationSeconds(duration time.Duration)
+}
+
 // MaxNodeSkipEvalTime is a time tracker for the biggest evaluation time of a node during ScaleDown
 type MaxNodeSkipEvalTime struct {
 	// lastEvalTime is the time of previous currentlyUnneededNodeNames parsing
 	lastEvalTime time.Time
 	// nodeNamesWithTimeStamps is maps of nodeNames with their time of last successful evaluation
 	nodeNamesWithTimeStamps map[string]time.Time
+
+	metrics metricObserver
 }
 
 // NewMaxNodeSkipEvalTime returns LongestNodeScaleDownEvalTime with lastEvalTime set to currentTime
 func NewMaxNodeSkipEvalTime(currentTime time.Time) *MaxNodeSkipEvalTime {
-	return &MaxNodeSkipEvalTime{lastEvalTime: currentTime}
+	return &MaxNodeSkipEvalTime{lastEvalTime: currentTime, metrics: metrics.DefaultMetrics}
 }
 
 // Retrieves the time of the last evaluation of a node.
@@ -65,6 +71,6 @@ func (l *MaxNodeSkipEvalTime) Update(nodeNames []string, currentTime time.Time)
 	l.lastEvalTime = currentTime
 	minimumTime := l.getMin()
 	longestDuration := currentTime.Sub(minimumTime)
-	metrics.ObserveMaxNodeSkipEvalDurationSeconds(longestDuration)
+	l.metrics.ObserveMaxNodeSkipEvalDurationSeconds(longestDuration)
 	return longestDuration
 }

cluster-autoscaler/core/scaledown/nodeevaltracker/max_node_skip_eval_time_test.go

@@ -21,8 +21,21 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
 )
 
+type mockMetrics struct {
+	mock.Mock
+}
+
+func (m *mockMetrics) ObserveMaxNodeSkipEvalDurationSeconds(duration time.Duration) {
+	m.Called(duration)
+}
+
+func newMaxNodeSkipEvalTime(currentTime time.Time, metrics metricObserver) *MaxNodeSkipEvalTime {
+	return &MaxNodeSkipEvalTime{lastEvalTime: currentTime, metrics: metrics}
+}
+
 func TestMaxNodeSkipEvalTime(t *testing.T) {
 	type testCase struct {
 		name                       string
@@ -66,11 +79,15 @@ func TestMaxNodeSkipEvalTime(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 			timestamp := start
-			maxNodeSkipEvalTime := NewMaxNodeSkipEvalTime(start)
+			mockMetrics := &mockMetrics{}
+			maxNodeSkipEvalTime := newMaxNodeSkipEvalTime(start, mockMetrics)
+			mockMetrics.On("ObserveMaxNodeSkipEvalDurationSeconds", mock.Anything).Return()
+
 			for i := 0; i < len(tc.unprocessedNodes); i++ {
 				timestamp = timestamp.Add(1 * time.Second)
 				assert.Equal(t, time.Duration(tc.wantMaxSkipEvalTimeSeconds[i])*time.Second, maxNodeSkipEvalTime.Update(tc.unprocessedNodes[i], timestamp))
 				assert.Equal(t, len(tc.unprocessedNodes[i]), len(maxNodeSkipEvalTime.nodeNamesWithTimeStamps))
+				mockMetrics.AssertCalled(t, "ObserveMaxNodeSkipEvalDurationSeconds", time.Duration(tc.wantMaxSkipEvalTimeSeconds[i])*time.Second)
 			}
 		})
 	}