Avoid containerd access as much as possible.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/store/sandbox/status_test.go

@@ -0,0 +1,61 @@
+/*
+Copyright 2018 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 sandbox
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	assertlib "github.com/stretchr/testify/assert"
+)
+
+func TestStatus(t *testing.T) {
+	testStatus := Status{
+		Pid:       123,
+		CreatedAt: time.Now(),
+		State:     StateUnknown,
+	}
+	updateStatus := Status{
+		Pid:       456,
+		CreatedAt: time.Now(),
+		State:     StateReady,
+	}
+	updateErr := errors.New("update error")
+	assert := assertlib.New(t)
+
+	t.Logf("simple store and get")
+	s := StoreStatus(testStatus)
+	old := s.Get()
+	assert.Equal(testStatus, old)
+
+	t.Logf("failed update should not take effect")
+	err := s.Update(func(o Status) (Status, error) {
+		o = updateStatus
+		return o, updateErr
+	})
+	assert.Equal(updateErr, err)
+	assert.Equal(testStatus, s.Get())
+
+	t.Logf("successful update should take effect but not checkpoint")
+	err = s.Update(func(o Status) (Status, error) {
+		o = updateStatus
+		return o, nil
+	})
+	assert.NoError(err)
+	assert.Equal(updateStatus, s.Get())
+}