diff --git a/cmd/kubeadm/app/phases/patchnode/BUILD b/cmd/kubeadm/app/phases/patchnode/BUILD
index 1ed8dfc9d16..a7aed14209a 100644
--- a/cmd/kubeadm/app/phases/patchnode/BUILD
+++ b/cmd/kubeadm/app/phases/patchnode/BUILD
@@ -1,4 +1,4 @@
-load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "go_default_library",
@@ -27,3 +27,16 @@ filegroup(
     tags = ["automanaged"],
     visibility = ["//visibility:public"],
 )
+
+go_test(
+    name = "go_default_test",
+    srcs = ["patchnode_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//cmd/kubeadm/app/constants:go_default_library",
+        "//staging/src/k8s.io/api/core/v1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
+        "//staging/src/k8s.io/client-go/kubernetes:go_default_library",
+        "//staging/src/k8s.io/client-go/rest:go_default_library",
+    ],
+)
diff --git a/cmd/kubeadm/app/phases/patchnode/patchnode_test.go b/cmd/kubeadm/app/phases/patchnode/patchnode_test.go
new file mode 100644
index 00000000000..93787be0f17
--- /dev/null
+++ b/cmd/kubeadm/app/phases/patchnode/patchnode_test.go
@@ -0,0 +1,124 @@
+/*
+Copyright 2020 The Kubernetes 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 patchnode
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	clientset "k8s.io/client-go/kubernetes"
+	restclient "k8s.io/client-go/rest"
+	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
+)
+
+func TestAnnotateCRISocket(t *testing.T) {
+	tests := []struct {
+		name                       string
+		currentCRISocketAnnotation string
+		newCRISocketAnnotation     string
+		expectedPatch              string
+	}{
+		{
+			name:                       "CRI-socket annotation missing",
+			currentCRISocketAnnotation: "",
+			newCRISocketAnnotation:     "/run/containerd/containerd.sock",
+			expectedPatch:              `{"metadata":{"annotations":{"kubeadm.alpha.kubernetes.io/cri-socket":"/run/containerd/containerd.sock"}}}`,
+		},
+		{
+			name:                       "CRI-socket annotation already exists",
+			currentCRISocketAnnotation: "/run/containerd/containerd.sock",
+			newCRISocketAnnotation:     "/run/containerd/containerd.sock",
+			expectedPatch:              `{}`,
+		},
+		{
+			name:                       "CRI-socket annotation needs to be updated",
+			currentCRISocketAnnotation: "/var/run/dockershim.sock",
+			newCRISocketAnnotation:     "/run/containerd/containerd.sock",
+			expectedPatch:              `{"metadata":{"annotations":{"kubeadm.alpha.kubernetes.io/cri-socket":"/run/containerd/containerd.sock"}}}`,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+
+			nodename := "node01"
+			node := &v1.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: nodename,
+					Labels: map[string]string{
+						v1.LabelHostname: nodename,
+					},
+					Annotations: map[string]string{},
+				},
+			}
+
+			if tc.currentCRISocketAnnotation != "" {
+				node.ObjectMeta.Annotations[kubeadmconstants.AnnotationKubeadmCRISocket] = tc.currentCRISocketAnnotation
+			}
+
+			jsonNode, err := json.Marshal(node)
+			if err != nil {
+				t.Fatalf("unexpected encoding error: %v", err)
+			}
+
+			var patchRequest string
+			s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				w.Header().Set("Content-Type", "application/json")
+
+				if req.URL.Path != "/api/v1/nodes/"+nodename {
+					t.Errorf("request for unexpected HTTP resource: %v", req.URL.Path)
+					http.Error(w, "", http.StatusNotFound)
+					return
+				}
+
+				switch req.Method {
+				case "GET":
+				case "PATCH":
+					buf := new(bytes.Buffer)
+					buf.ReadFrom(req.Body)
+					patchRequest = buf.String()
+				default:
+					t.Errorf("request for unexpected HTTP verb: %v", req.Method)
+					http.Error(w, "", http.StatusNotFound)
+					return
+				}
+
+				w.WriteHeader(http.StatusOK)
+				w.Write(jsonNode)
+			}))
+			defer s.Close()
+
+			cs, err := clientset.NewForConfig(&restclient.Config{Host: s.URL})
+			if err != nil {
+				t.Fatalf("unexpected error building clientset: %v", err)
+			}
+
+			if err := AnnotateCRISocket(cs, nodename, tc.newCRISocketAnnotation); err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+
+			if tc.expectedPatch != patchRequest {
+				t.Errorf("expected patch %v, got %v", tc.expectedPatch, patchRequest)
+			}
+		})
+	}
+}