Refactor usageNanoCores be to used for all OSes

Signed-off-by: James Sturtevant <jstur@microsoft.com>

pkg/cri/server/container_stats_list_test.go

@@ -0,0 +1,74 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package server
+
+import (
+	"testing"
+	"time"
+
+	containerstore "github.com/containerd/containerd/pkg/cri/store/container"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestContainerMetricsCPUNanoCoreUsage(t *testing.T) {
+	c := newTestCRIService()
+	timestamp := time.Now()
+	secondAfterTimeStamp := timestamp.Add(time.Second)
+	ID := "ID"
+
+	for desc, test := range map[string]struct {
+		firstCPUValue               uint64
+		secondCPUValue              uint64
+		expectedNanoCoreUsageFirst  uint64
+		expectedNanoCoreUsageSecond uint64
+	}{
+		"metrics": {
+			firstCPUValue:               50,
+			secondCPUValue:              500,
+			expectedNanoCoreUsageFirst:  0,
+			expectedNanoCoreUsageSecond: 450,
+		},
+	} {
+		t.Run(desc, func(t *testing.T) {
+			container, err := containerstore.NewContainer(
+				containerstore.Metadata{ID: ID},
+			)
+			assert.NoError(t, err)
+			assert.Nil(t, container.Stats)
+			err = c.containerStore.Add(container)
+			assert.NoError(t, err)
+
+			cpuUsage, err := c.getUsageNanoCores(ID, false, test.firstCPUValue, timestamp)
+			assert.NoError(t, err)
+
+			container, err = c.containerStore.Get(ID)
+			assert.NoError(t, err)
+			assert.NotNil(t, container.Stats)
+
+			assert.Equal(t, test.expectedNanoCoreUsageFirst, cpuUsage)
+
+			cpuUsage, err = c.getUsageNanoCores(ID, false, test.secondCPUValue, secondAfterTimeStamp)
+			assert.NoError(t, err)
+			assert.Equal(t, test.expectedNanoCoreUsageSecond, cpuUsage)
+
+			container, err = c.containerStore.Get(ID)
+			assert.NoError(t, err)
+			assert.NotNil(t, container.Stats)
+		})
+	}
+
+}