checkpointer: add test case asserting behavior.

The checkpointer will activate a checkpoint if the local kubelet API
parent exists but the CRI shim doesn't report it running. We may want
to change this later, but this is the current behavior.

Also make the stop and remove orders stable to make the tests
consistently pass and also because why not.

Author: diegs

pkg/checkpoint/process.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"sort"
 	"time"
 
 	"github.com/golang/glog"
@@ -143,6 +144,7 @@ func (cs *checkpoints) process(now time.Time, apiAvailable bool, localRunningPod
 					stops = append(stops, name)
 				}
 			}
+			sort.Strings(stops) // Ensure stable ordering.
 			stops = append(stops, cs.selfCheckpoint.name)
 			return starts, stops, removes
 		case remove:
@@ -154,6 +156,7 @@ func (cs *checkpoints) process(now time.Time, apiAvailable bool, localRunningPod
 					delete(cs.checkpoints, name)
 				}
 			}
+			sort.Strings(removes) // Ensure stable ordering.
 			removes = append(removes, cs.selfCheckpoint.name)
 			delete(cs.checkpoints, cs.selfCheckpoint.name)
 			cs.selfCheckpoint = nil

pkg/checkpoint/process_test.go

@@ -55,6 +55,13 @@ func TestProcess(t *testing.T) {
 			apiParents:          map[string]*v1.Pod{"AA": {}},
 			expectStart:         []string{"AA"},
 		},
+		{
+			desc:                "Inactive checkpoint and only api and kubelet parents: should start",
+			inactiveCheckpoints: map[string]*v1.Pod{"AA": {}},
+			apiParents:          map[string]*v1.Pod{"AA": {}},
+			localParents:        map[string]*v1.Pod{"AA": {}},
+			expectStart:         []string{"AA"},
+		},
 		{
 			desc:              "Active checkpoint and no local running: no change",
 			activeCheckpoints: map[string]*v1.Pod{"AA": {}},