diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.bind_device_to_gateway.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.bind_device_to_gateway.js
index e5d0348f48d..8c901cc01a9 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.bind_device_to_gateway.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.bind_device_to_gateway.js
@@ -23,6 +23,9 @@
 function main(parent, gatewayId, deviceId) {
   // [START cloudiot_v1_generated_DeviceManager_BindDeviceToGateway_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.create_device.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.create_device.js
index d38142b0f46..ee99565e08a 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.create_device.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.create_device.js
@@ -23,6 +23,9 @@
 function main(parent, device) {
   // [START cloudiot_v1_generated_DeviceManager_CreateDevice_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.create_device_registry.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.create_device_registry.js
index 6248800bb40..7ea4129928b 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.create_device_registry.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.create_device_registry.js
@@ -23,6 +23,9 @@
 function main(parent, deviceRegistry) {
   // [START cloudiot_v1_generated_DeviceManager_CreateDeviceRegistry_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.delete_device.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.delete_device.js
index ab1999e2b67..e981a8a7a01 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.delete_device.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.delete_device.js
@@ -23,6 +23,9 @@
 function main(name) {
   // [START cloudiot_v1_generated_DeviceManager_DeleteDevice_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.delete_device_registry.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.delete_device_registry.js
index 663be451d24..37f5d2ad2ea 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.delete_device_registry.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.delete_device_registry.js
@@ -23,6 +23,9 @@
 function main(name) {
   // [START cloudiot_v1_generated_DeviceManager_DeleteDeviceRegistry_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.get_device.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.get_device.js
index db5022fb8fe..97bdebc68ab 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.get_device.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.get_device.js
@@ -23,6 +23,9 @@
 function main(name) {
   // [START cloudiot_v1_generated_DeviceManager_GetDevice_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.get_device_registry.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.get_device_registry.js
index 7cbb7241bc3..2ec184f4858 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.get_device_registry.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.get_device_registry.js
@@ -23,6 +23,9 @@
 function main(name) {
   // [START cloudiot_v1_generated_DeviceManager_GetDeviceRegistry_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.get_iam_policy.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.get_iam_policy.js
index 039b3941163..05f5ad9f0ec 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.get_iam_policy.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.get_iam_policy.js
@@ -23,6 +23,9 @@
 function main(resource) {
   // [START cloudiot_v1_generated_DeviceManager_GetIamPolicy_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_config_versions.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_config_versions.js
index be6a024d4c9..2b4d1e0189e 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_config_versions.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_config_versions.js
@@ -23,6 +23,9 @@
 function main(name) {
   // [START cloudiot_v1_generated_DeviceManager_ListDeviceConfigVersions_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_registries.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_registries.js
index d7853e34aa2..344f409e391 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_registries.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_registries.js
@@ -23,6 +23,9 @@
 function main(parent) {
   // [START cloudiot_v1_generated_DeviceManager_ListDeviceRegistries_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_states.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_states.js
index d9c8519d01d..a6323204556 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_states.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.list_device_states.js
@@ -23,6 +23,9 @@
 function main(name) {
   // [START cloudiot_v1_generated_DeviceManager_ListDeviceStates_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.list_devices.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.list_devices.js
index 7e33937aaa9..f8751e6cea2 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.list_devices.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.list_devices.js
@@ -23,6 +23,9 @@
 function main(parent) {
   // [START cloudiot_v1_generated_DeviceManager_ListDevices_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.modify_cloud_to_device_config.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.modify_cloud_to_device_config.js
index 9e415682954..8a6968b0f4e 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.modify_cloud_to_device_config.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.modify_cloud_to_device_config.js
@@ -23,6 +23,9 @@
 function main(name, binaryData) {
   // [START cloudiot_v1_generated_DeviceManager_ModifyCloudToDeviceConfig_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.send_command_to_device.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.send_command_to_device.js
index df3997168a9..ba46cd8da18 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.send_command_to_device.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.send_command_to_device.js
@@ -23,6 +23,9 @@
 function main(name, binaryData) {
   // [START cloudiot_v1_generated_DeviceManager_SendCommandToDevice_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.set_iam_policy.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.set_iam_policy.js
index 05ba74e3704..87f44955f5e 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.set_iam_policy.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.set_iam_policy.js
@@ -23,6 +23,9 @@
 function main(resource, policy) {
   // [START cloudiot_v1_generated_DeviceManager_SetIamPolicy_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.test_iam_permissions.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.test_iam_permissions.js
index 81f299d385f..d13cb26b7d4 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.test_iam_permissions.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.test_iam_permissions.js
@@ -23,6 +23,9 @@
 function main(resource, permissions) {
   // [START cloudiot_v1_generated_DeviceManager_TestIamPermissions_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.unbind_device_from_gateway.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.unbind_device_from_gateway.js
index 37fb81b5d88..5341f2f0681 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.unbind_device_from_gateway.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.unbind_device_from_gateway.js
@@ -23,6 +23,9 @@
 function main(parent, gatewayId, deviceId) {
   // [START cloudiot_v1_generated_DeviceManager_UnbindDeviceFromGateway_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.update_device.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.update_device.js
index f2c217889f9..62a144d11c9 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.update_device.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.update_device.js
@@ -23,6 +23,9 @@
 function main(device, updateMask) {
   // [START cloudiot_v1_generated_DeviceManager_UpdateDevice_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/device_manager.update_device_registry.js b/packages/google-cloud-iot/samples/generated/v1/device_manager.update_device_registry.js
index c3a34b16258..06843ef1dd2 100644
--- a/packages/google-cloud-iot/samples/generated/v1/device_manager.update_device_registry.js
+++ b/packages/google-cloud-iot/samples/generated/v1/device_manager.update_device_registry.js
@@ -23,6 +23,9 @@
 function main(deviceRegistry, updateMask) {
   // [START cloudiot_v1_generated_DeviceManager_UpdateDeviceRegistry_async]
   /**
+   * This snippet has been automatically generated and should be regarded as a code template only.
+   * It will require modifications to work.
+   * It may require correct/in-range values for request initialization.
    * TODO(developer): Uncomment these variables before running the sample.
    */
   /**
diff --git a/packages/google-cloud-iot/samples/generated/v1/snippet_metadata.google.cloud.iot.v1.json b/packages/google-cloud-iot/samples/generated/v1/snippet_metadata.google.cloud.iot.v1.json
index 13c5a252b48..f3a41c0f895 100644
--- a/packages/google-cloud-iot/samples/generated/v1/snippet_metadata.google.cloud.iot.v1.json
+++ b/packages/google-cloud-iot/samples/generated/v1/snippet_metadata.google.cloud.iot.v1.json
@@ -22,7 +22,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 58,
+                    "end": 61,
                     "type": "FULL"
                 }
             ],
@@ -66,7 +66,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 51,
+                    "end": 54,
                     "type": "FULL"
                 }
             ],
@@ -106,7 +106,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 61,
+                    "end": 64,
                     "type": "FULL"
                 }
             ],
@@ -150,7 +150,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 51,
+                    "end": 54,
                     "type": "FULL"
                 }
             ],
@@ -190,7 +190,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 66,
+                    "end": 69,
                     "type": "FULL"
                 }
             ],
@@ -238,7 +238,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 59,
+                    "end": 62,
                     "type": "FULL"
                 }
             ],
@@ -282,7 +282,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 58,
+                    "end": 61,
                     "type": "FULL"
                 }
             ],
@@ -326,7 +326,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 61,
+                    "end": 64,
                     "type": "FULL"
                 }
             ],
@@ -370,7 +370,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 52,
+                    "end": 55,
                     "type": "FULL"
                 }
             ],
@@ -410,7 +410,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 87,
+                    "end": 90,
                     "type": "FULL"
                 }
             ],
@@ -474,7 +474,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 65,
+                    "end": 68,
                     "type": "FULL"
                 }
             ],
@@ -522,7 +522,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 58,
+                    "end": 61,
                     "type": "FULL"
                 }
             ],
@@ -566,7 +566,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 58,
+                    "end": 61,
                     "type": "FULL"
                 }
             ],
@@ -610,7 +610,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 66,
+                    "end": 69,
                     "type": "FULL"
                 }
             ],
@@ -658,7 +658,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 56,
+                    "end": 59,
                     "type": "FULL"
                 }
             ],
@@ -702,7 +702,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 59,
+                    "end": 62,
                     "type": "FULL"
                 }
             ],
@@ -746,7 +746,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 65,
+                    "end": 68,
                     "type": "FULL"
                 }
             ],
@@ -794,7 +794,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 64,
+                    "end": 67,
                     "type": "FULL"
                 }
             ],
@@ -842,7 +842,7 @@
             "segments": [
                 {
                     "start": 25,
-                    "end": 64,
+                    "end": 67,
                     "type": "FULL"
                 }
             ],
diff --git a/packages/google-cloud-iot/src/v1/device_manager_client.ts b/packages/google-cloud-iot/src/v1/device_manager_client.ts
index 948db8bca6e..3b85af18e64 100644
--- a/packages/google-cloud-iot/src/v1/device_manager_client.ts
+++ b/packages/google-cloud-iot/src/v1/device_manager_client.ts
@@ -28,7 +28,6 @@ import {
 } from 'google-gax';
 
 import {Transform} from 'stream';
-import {RequestType} from 'google-gax/build/src/apitypes';
 import * as protos from '../../protos/protos';
 import jsonProtos = require('../../protos/protos.json');
 /**
@@ -279,7 +278,8 @@ export class DeviceManagerClient {
       const apiCall = this._gaxModule.createApiCall(
         callPromise,
         this._defaults[methodName],
-        descriptor
+        descriptor,
+        this._opts.fallback
       );
 
       this.innerApiCalls[methodName] = apiCall;
@@ -2101,7 +2101,7 @@ export class DeviceManagerClient {
     const callSettings = defaultCallSettings.merge(options);
     this.initialize();
     return this.descriptors.page.listDeviceRegistries.createStream(
-      this.innerApiCalls.listDeviceRegistries as gax.GaxCall,
+      this.innerApiCalls.listDeviceRegistries as GaxCall,
       request,
       callSettings
     );
@@ -2155,7 +2155,7 @@ export class DeviceManagerClient {
     this.initialize();
     return this.descriptors.page.listDeviceRegistries.asyncIterate(
       this.innerApiCalls['listDeviceRegistries'] as GaxCall,
-      request as unknown as RequestType,
+      request as {},
       callSettings
     ) as AsyncIterable<protos.google.cloud.iot.v1.IDeviceRegistry>;
   }
@@ -2326,7 +2326,7 @@ export class DeviceManagerClient {
     const callSettings = defaultCallSettings.merge(options);
     this.initialize();
     return this.descriptors.page.listDevices.createStream(
-      this.innerApiCalls.listDevices as gax.GaxCall,
+      this.innerApiCalls.listDevices as GaxCall,
       request,
       callSettings
     );
@@ -2393,7 +2393,7 @@ export class DeviceManagerClient {
     this.initialize();
     return this.descriptors.page.listDevices.asyncIterate(
       this.innerApiCalls['listDevices'] as GaxCall,
-      request as unknown as RequestType,
+      request as {},
       callSettings
     ) as AsyncIterable<protos.google.cloud.iot.v1.IDevice>;
   }
diff --git a/packages/google-cloud-iot/test/gapic_device_manager_v1.ts b/packages/google-cloud-iot/test/gapic_device_manager_v1.ts
index d2d77742070..de9ed0370c2 100644
--- a/packages/google-cloud-iot/test/gapic_device_manager_v1.ts
+++ b/packages/google-cloud-iot/test/gapic_device_manager_v1.ts
@@ -113,99 +113,103 @@ function stubAsyncIterationCall<ResponseType>(
 }
 
 describe('v1.DeviceManagerClient', () => {
-  it('has servicePath', () => {
-    const servicePath = devicemanagerModule.v1.DeviceManagerClient.servicePath;
-    assert(servicePath);
-  });
-
-  it('has apiEndpoint', () => {
-    const apiEndpoint = devicemanagerModule.v1.DeviceManagerClient.apiEndpoint;
-    assert(apiEndpoint);
-  });
-
-  it('has port', () => {
-    const port = devicemanagerModule.v1.DeviceManagerClient.port;
-    assert(port);
-    assert(typeof port === 'number');
-  });
+  describe('Common methods', () => {
+    it('has servicePath', () => {
+      const servicePath =
+        devicemanagerModule.v1.DeviceManagerClient.servicePath;
+      assert(servicePath);
+    });
 
-  it('should create a client with no option', () => {
-    const client = new devicemanagerModule.v1.DeviceManagerClient();
-    assert(client);
-  });
+    it('has apiEndpoint', () => {
+      const apiEndpoint =
+        devicemanagerModule.v1.DeviceManagerClient.apiEndpoint;
+      assert(apiEndpoint);
+    });
 
-  it('should create a client with gRPC fallback', () => {
-    const client = new devicemanagerModule.v1.DeviceManagerClient({
-      fallback: true,
+    it('has port', () => {
+      const port = devicemanagerModule.v1.DeviceManagerClient.port;
+      assert(port);
+      assert(typeof port === 'number');
     });
-    assert(client);
-  });
 
-  it('has initialize method and supports deferred initialization', async () => {
-    const client = new devicemanagerModule.v1.DeviceManagerClient({
-      credentials: {client_email: 'bogus', private_key: 'bogus'},
-      projectId: 'bogus',
+    it('should create a client with no option', () => {
+      const client = new devicemanagerModule.v1.DeviceManagerClient();
+      assert(client);
     });
-    assert.strictEqual(client.deviceManagerStub, undefined);
-    await client.initialize();
-    assert(client.deviceManagerStub);
-  });
 
-  it('has close method for the initialized client', done => {
-    const client = new devicemanagerModule.v1.DeviceManagerClient({
-      credentials: {client_email: 'bogus', private_key: 'bogus'},
-      projectId: 'bogus',
+    it('should create a client with gRPC fallback', () => {
+      const client = new devicemanagerModule.v1.DeviceManagerClient({
+        fallback: true,
+      });
+      assert(client);
     });
-    client.initialize();
-    assert(client.deviceManagerStub);
-    client.close().then(() => {
-      done();
+
+    it('has initialize method and supports deferred initialization', async () => {
+      const client = new devicemanagerModule.v1.DeviceManagerClient({
+        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        projectId: 'bogus',
+      });
+      assert.strictEqual(client.deviceManagerStub, undefined);
+      await client.initialize();
+      assert(client.deviceManagerStub);
     });
-  });
 
-  it('has close method for the non-initialized client', done => {
-    const client = new devicemanagerModule.v1.DeviceManagerClient({
-      credentials: {client_email: 'bogus', private_key: 'bogus'},
-      projectId: 'bogus',
+    it('has close method for the initialized client', done => {
+      const client = new devicemanagerModule.v1.DeviceManagerClient({
+        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        projectId: 'bogus',
+      });
+      client.initialize();
+      assert(client.deviceManagerStub);
+      client.close().then(() => {
+        done();
+      });
     });
-    assert.strictEqual(client.deviceManagerStub, undefined);
-    client.close().then(() => {
-      done();
+
+    it('has close method for the non-initialized client', done => {
+      const client = new devicemanagerModule.v1.DeviceManagerClient({
+        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        projectId: 'bogus',
+      });
+      assert.strictEqual(client.deviceManagerStub, undefined);
+      client.close().then(() => {
+        done();
+      });
     });
-  });
 
-  it('has getProjectId method', async () => {
-    const fakeProjectId = 'fake-project-id';
-    const client = new devicemanagerModule.v1.DeviceManagerClient({
-      credentials: {client_email: 'bogus', private_key: 'bogus'},
-      projectId: 'bogus',
+    it('has getProjectId method', async () => {
+      const fakeProjectId = 'fake-project-id';
+      const client = new devicemanagerModule.v1.DeviceManagerClient({
+        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        projectId: 'bogus',
+      });
+      client.auth.getProjectId = sinon.stub().resolves(fakeProjectId);
+      const result = await client.getProjectId();
+      assert.strictEqual(result, fakeProjectId);
+      assert((client.auth.getProjectId as SinonStub).calledWithExactly());
     });
-    client.auth.getProjectId = sinon.stub().resolves(fakeProjectId);
-    const result = await client.getProjectId();
-    assert.strictEqual(result, fakeProjectId);
-    assert((client.auth.getProjectId as SinonStub).calledWithExactly());
-  });
 
-  it('has getProjectId method with callback', async () => {
-    const fakeProjectId = 'fake-project-id';
-    const client = new devicemanagerModule.v1.DeviceManagerClient({
-      credentials: {client_email: 'bogus', private_key: 'bogus'},
-      projectId: 'bogus',
-    });
-    client.auth.getProjectId = sinon
-      .stub()
-      .callsArgWith(0, null, fakeProjectId);
-    const promise = new Promise((resolve, reject) => {
-      client.getProjectId((err?: Error | null, projectId?: string | null) => {
-        if (err) {
-          reject(err);
-        } else {
-          resolve(projectId);
-        }
+    it('has getProjectId method with callback', async () => {
+      const fakeProjectId = 'fake-project-id';
+      const client = new devicemanagerModule.v1.DeviceManagerClient({
+        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        projectId: 'bogus',
+      });
+      client.auth.getProjectId = sinon
+        .stub()
+        .callsArgWith(0, null, fakeProjectId);
+      const promise = new Promise((resolve, reject) => {
+        client.getProjectId((err?: Error | null, projectId?: string | null) => {
+          if (err) {
+            reject(err);
+          } else {
+            resolve(projectId);
+          }
+        });
       });
+      const result = await promise;
+      assert.strictEqual(result, fakeProjectId);
     });
-    const result = await promise;
-    assert.strictEqual(result, fakeProjectId);
   });
 
   describe('createDeviceRegistry', () => {