Fixes tests with correct assumptions

pkg/api/version/version.go

@@ -33,6 +33,7 @@ var (
 	instanceTimeout                        = 1 * time.Minute
 	_                 memberlist.Mergeable = (*Versions)(nil)
 	_                 services.Service     = (*Service)(nil)
+	now                                    = time.Now
 )
 
 func GetCodec() codec.Codec {
@@ -63,7 +64,7 @@ func (v *Versions) Marshal() ([]byte, error) {
 
 // Merge merges two versions. This is used when CASing or merging versions from other nodes.
 // v is the local version and should be mutated to include the changes from incoming.
-// The returned value is the change to broadcast.
+// The function should only returned changed instances.
 func (v *Versions) Merge(incoming memberlist.Mergeable, localCAS bool) (memberlist.Mergeable, error) {
 	if incoming == nil {
 		return nil, nil
@@ -107,7 +108,7 @@ func (v *Versions) Merge(incoming memberlist.Mergeable, localCAS bool) (memberli
 		for k, current := range v.Instances {
 			if _, ok := other.Instances[k]; !ok && !current.Left {
 				current.Left = true
-				current.Timestamp = time.Now().UnixNano()
+				current.Timestamp = now().UnixNano()
 				updated = append(updated, k)
 			}
 		}
@@ -138,7 +139,7 @@ func (d *Versions) MergeContent() []string {
 func (v *Versions) RemoveTombstones(limit time.Time) (total, removed int) {
 	for n, inst := range v.Instances {
 		if inst.Left {
-			if limit.IsZero() || time.Unix(inst.Timestamp, 0).Before(limit) {
+			if limit.IsZero() || time.Unix(0, inst.Timestamp).Before(limit) {
 				// remove it
 				delete(v.Instances, n)
 				removed++
@@ -246,7 +247,7 @@ func (svc *Service) heartbeat(ctx context.Context) error {
 		}
 		current.Addr = svc.addr
 		current.ID = svc.id
-		current.Timestamp = time.Now().UnixNano()
+		current.Timestamp = now().UnixNano()
 		current.QuerierAPI = svc.version
 		// Now prune old instances.
 		for id, instance := range versions.Instances {

pkg/api/version/version_test.go

@@ -157,7 +157,16 @@ func TestVersionsMultiple(t *testing.T) {
 	expectVersion(t, 2)
 }
 
+var nowTs = time.Now().UnixNano()
+
 func TestMerge(t *testing.T) {
+	now = func() time.Time {
+		return time.Unix(0, nowTs)
+	}
+	t.Cleanup(func() {
+		now = time.Now
+	})
+
 	for name, tc := range map[string]struct {
 		base     *Versions
 		incoming memberlist.Mergeable
@@ -200,7 +209,6 @@ func TestMerge(t *testing.T) {
 				createVersion(t, "2", 3),
 			),
 			expected: createVersions(t,
-				createVersion(t, "1", 1),
 				createVersion(t, "2", 3),
 			),
 		},
@@ -213,7 +221,6 @@ func TestMerge(t *testing.T) {
 				createVersion(t, "2", 2),
 			),
 			expected: createVersions(t,
-				createVersion(t, "1", 1),
 				createVersion(t, "2", 2),
 			),
 		},
@@ -226,7 +233,7 @@ func TestMerge(t *testing.T) {
 				createVersion(t, "1", 1),
 			),
 			expected: createVersions(t,
-				createVersion(t, "1", 1),
+				createLeftVersion(t, "2", nowTs),
 			),
 		},
 		"instance removed and added": {
@@ -240,7 +247,7 @@ func TestMerge(t *testing.T) {
 			),
 			expected: createVersions(t,
 				createVersion(t, "3", 3),
-				createVersion(t, "2", 2),
+				createLeftVersion(t, "1", nowTs),
 			),
 		},
 	} {
@@ -254,6 +261,15 @@ func TestMerge(t *testing.T) {
 	}
 }
 
+func createLeftVersion(t *testing.T, id string, ts int64) *versionv1.InstanceVersion {
+	t.Helper()
+	return &versionv1.InstanceVersion{
+		ID:        id,
+		Timestamp: ts,
+		Left:      true,
+	}
+}
+
 func createVersion(t *testing.T, id string, ts int64) *versionv1.InstanceVersion {
 	t.Helper()
 	return &versionv1.InstanceVersion{