[node operator] patching util functions

Signed-off-by: Malte Poll <mp@edgeless.systems>

operators/constellation-node-operator/internal/patch/labels_test.go

@@ -0,0 +1,59 @@
+package patch
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	corev1 "k8s.io/api/core/v1"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+var labelsTestObject = corev1.Node{
+	TypeMeta: v1.TypeMeta{
+		Kind:       "Node",
+		APIVersion: "v1",
+	},
+	ObjectMeta: v1.ObjectMeta{
+		ResourceVersion: "0",
+	},
+}
+
+func TestSetLabels(t *testing.T) {
+	testCases := map[string]struct {
+		oldLabels map[string]string
+		newLabels map[string]string
+		wantPatch []byte
+	}{
+		"empty patch only contains resource version": {
+			wantPatch: []byte(`{"metadata":{"resourceVersion":"0"}}`),
+		},
+		"patch on node without existing labels": {
+			newLabels: map[string]string{"key": "value"},
+			wantPatch: []byte(`{"metadata":{"labels":{"key":"value"},"resourceVersion":"0"}}`),
+		},
+		"patch on node with same existing labels": {
+			oldLabels: map[string]string{"key": "value"},
+			newLabels: map[string]string{"key": "value"},
+			wantPatch: []byte(`{"metadata":{"resourceVersion":"0"}}`),
+		},
+		"patch on node with same key but different value": {
+			oldLabels: map[string]string{"key": "oldvalue"},
+			newLabels: map[string]string{"key": "newvalue"},
+			wantPatch: []byte(`{"metadata":{"labels":{"key":"newvalue"},"resourceVersion":"0"}}`),
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			original := labelsTestObject.DeepCopy()
+			original.SetLabels(tc.oldLabels)
+			patched := original.DeepCopy()
+			patch := SetLabels(original, patched, tc.newLabels)
+			data, err := patch.Data(patched)
+			assert.NoError(err)
+			assert.Equal(tc.wantPatch, data)
+		})
+	}
+}