diff --git a/packages/google-cloud-documentai/src/v1/document_processor_service_client.ts b/packages/google-cloud-documentai/src/v1/document_processor_service_client.ts
index dff16ac1453..32e602d352d 100644
--- a/packages/google-cloud-documentai/src/v1/document_processor_service_client.ts
+++ b/packages/google-cloud-documentai/src/v1/document_processor_service_client.ts
@@ -48,6 +48,7 @@ const version = require('../../../package.json').version;
 export class DocumentProcessorServiceClient {
   private _terminated = false;
   private _opts: ClientOptions;
+  private _providedCustomServicePath: boolean;
   private _gaxModule: typeof gax | typeof gax.fallback;
   private _gaxGrpc: gax.GrpcClient | gax.fallback.GrpcClient;
   private _protos: {};
@@ -59,6 +60,7 @@ export class DocumentProcessorServiceClient {
     longrunning: {},
     batching: {},
   };
+  warn: (code: string, message: string, warnType?: string) => void;
   innerApiCalls: {[name: string]: Function};
   pathTemplates: {[name: string]: gax.PathTemplate};
   operationsClient: gax.OperationsClient;
@@ -104,6 +106,9 @@ export class DocumentProcessorServiceClient {
       .constructor as typeof DocumentProcessorServiceClient;
     const servicePath =
       opts?.servicePath || opts?.apiEndpoint || staticMembers.servicePath;
+    this._providedCustomServicePath = !!(
+      opts?.servicePath || opts?.apiEndpoint
+    );
     const port = opts?.port || staticMembers.port;
     const clientConfig = opts?.clientConfig ?? {};
     const fallback =
@@ -210,6 +215,9 @@ export class DocumentProcessorServiceClient {
     // of calling the API is handled in `google-gax`, with this code
     // merely providing the destination and request information.
     this.innerApiCalls = {};
+
+    // Add a warn function to the client constructor so it can be easily tested.
+    this.warn = gax.warn;
   }
 
   /**
@@ -239,7 +247,8 @@ export class DocumentProcessorServiceClient {
         : // eslint-disable-next-line @typescript-eslint/no-explicit-any
           (this._protos as any).google.cloud.documentai.v1
             .DocumentProcessorService,
-      this._opts
+      this._opts,
+      this._providedCustomServicePath
     ) as Promise<{[method: string]: Function}>;
 
     // Iterate over each of the methods that the service provides
diff --git a/packages/google-cloud-documentai/src/v1beta1/document_understanding_service_client.ts b/packages/google-cloud-documentai/src/v1beta1/document_understanding_service_client.ts
index f7308e952c3..8a006d5e807 100644
--- a/packages/google-cloud-documentai/src/v1beta1/document_understanding_service_client.ts
+++ b/packages/google-cloud-documentai/src/v1beta1/document_understanding_service_client.ts
@@ -47,6 +47,7 @@ const version = require('../../../package.json').version;
 export class DocumentUnderstandingServiceClient {
   private _terminated = false;
   private _opts: ClientOptions;
+  private _providedCustomServicePath: boolean;
   private _gaxModule: typeof gax | typeof gax.fallback;
   private _gaxGrpc: gax.GrpcClient | gax.fallback.GrpcClient;
   private _protos: {};
@@ -58,6 +59,7 @@ export class DocumentUnderstandingServiceClient {
     longrunning: {},
     batching: {},
   };
+  warn: (code: string, message: string, warnType?: string) => void;
   innerApiCalls: {[name: string]: Function};
   operationsClient: gax.OperationsClient;
   documentUnderstandingServiceStub?: Promise<{[name: string]: Function}>;
@@ -102,6 +104,9 @@ export class DocumentUnderstandingServiceClient {
       .constructor as typeof DocumentUnderstandingServiceClient;
     const servicePath =
       opts?.servicePath || opts?.apiEndpoint || staticMembers.servicePath;
+    this._providedCustomServicePath = !!(
+      opts?.servicePath || opts?.apiEndpoint
+    );
     const port = opts?.port || staticMembers.port;
     const clientConfig = opts?.clientConfig ?? {};
     const fallback =
@@ -185,6 +190,9 @@ export class DocumentUnderstandingServiceClient {
     // of calling the API is handled in `google-gax`, with this code
     // merely providing the destination and request information.
     this.innerApiCalls = {};
+
+    // Add a warn function to the client constructor so it can be easily tested.
+    this.warn = gax.warn;
   }
 
   /**
@@ -214,7 +222,8 @@ export class DocumentUnderstandingServiceClient {
         : // eslint-disable-next-line @typescript-eslint/no-explicit-any
           (this._protos as any).google.cloud.documentai.v1beta1
             .DocumentUnderstandingService,
-      this._opts
+      this._opts,
+      this._providedCustomServicePath
     ) as Promise<{[method: string]: Function}>;
 
     // Iterate over each of the methods that the service provides
diff --git a/packages/google-cloud-documentai/src/v1beta2/document_understanding_service_client.ts b/packages/google-cloud-documentai/src/v1beta2/document_understanding_service_client.ts
index 663ae582931..ca4fb252d79 100644
--- a/packages/google-cloud-documentai/src/v1beta2/document_understanding_service_client.ts
+++ b/packages/google-cloud-documentai/src/v1beta2/document_understanding_service_client.ts
@@ -47,6 +47,7 @@ const version = require('../../../package.json').version;
 export class DocumentUnderstandingServiceClient {
   private _terminated = false;
   private _opts: ClientOptions;
+  private _providedCustomServicePath: boolean;
   private _gaxModule: typeof gax | typeof gax.fallback;
   private _gaxGrpc: gax.GrpcClient | gax.fallback.GrpcClient;
   private _protos: {};
@@ -58,6 +59,7 @@ export class DocumentUnderstandingServiceClient {
     longrunning: {},
     batching: {},
   };
+  warn: (code: string, message: string, warnType?: string) => void;
   innerApiCalls: {[name: string]: Function};
   operationsClient: gax.OperationsClient;
   documentUnderstandingServiceStub?: Promise<{[name: string]: Function}>;
@@ -102,6 +104,9 @@ export class DocumentUnderstandingServiceClient {
       .constructor as typeof DocumentUnderstandingServiceClient;
     const servicePath =
       opts?.servicePath || opts?.apiEndpoint || staticMembers.servicePath;
+    this._providedCustomServicePath = !!(
+      opts?.servicePath || opts?.apiEndpoint
+    );
     const port = opts?.port || staticMembers.port;
     const clientConfig = opts?.clientConfig ?? {};
     const fallback =
@@ -185,6 +190,9 @@ export class DocumentUnderstandingServiceClient {
     // of calling the API is handled in `google-gax`, with this code
     // merely providing the destination and request information.
     this.innerApiCalls = {};
+
+    // Add a warn function to the client constructor so it can be easily tested.
+    this.warn = gax.warn;
   }
 
   /**
@@ -214,7 +222,8 @@ export class DocumentUnderstandingServiceClient {
         : // eslint-disable-next-line @typescript-eslint/no-explicit-any
           (this._protos as any).google.cloud.documentai.v1beta2
             .DocumentUnderstandingService,
-      this._opts
+      this._opts,
+      this._providedCustomServicePath
     ) as Promise<{[method: string]: Function}>;
 
     // Iterate over each of the methods that the service provides
diff --git a/packages/google-cloud-documentai/src/v1beta3/document_processor_service_client.ts b/packages/google-cloud-documentai/src/v1beta3/document_processor_service_client.ts
index 60feb96b46a..44cb40c5e48 100644
--- a/packages/google-cloud-documentai/src/v1beta3/document_processor_service_client.ts
+++ b/packages/google-cloud-documentai/src/v1beta3/document_processor_service_client.ts
@@ -52,6 +52,7 @@ const version = require('../../../package.json').version;
 export class DocumentProcessorServiceClient {
   private _terminated = false;
   private _opts: ClientOptions;
+  private _providedCustomServicePath: boolean;
   private _gaxModule: typeof gax | typeof gax.fallback;
   private _gaxGrpc: gax.GrpcClient | gax.fallback.GrpcClient;
   private _protos: {};
@@ -63,6 +64,7 @@ export class DocumentProcessorServiceClient {
     longrunning: {},
     batching: {},
   };
+  warn: (code: string, message: string, warnType?: string) => void;
   innerApiCalls: {[name: string]: Function};
   pathTemplates: {[name: string]: gax.PathTemplate};
   operationsClient: gax.OperationsClient;
@@ -108,6 +110,9 @@ export class DocumentProcessorServiceClient {
       .constructor as typeof DocumentProcessorServiceClient;
     const servicePath =
       opts?.servicePath || opts?.apiEndpoint || staticMembers.servicePath;
+    this._providedCustomServicePath = !!(
+      opts?.servicePath || opts?.apiEndpoint
+    );
     const port = opts?.port || staticMembers.port;
     const clientConfig = opts?.clientConfig ?? {};
     const fallback =
@@ -267,6 +272,9 @@ export class DocumentProcessorServiceClient {
     // of calling the API is handled in `google-gax`, with this code
     // merely providing the destination and request information.
     this.innerApiCalls = {};
+
+    // Add a warn function to the client constructor so it can be easily tested.
+    this.warn = gax.warn;
   }
 
   /**
@@ -296,7 +304,8 @@ export class DocumentProcessorServiceClient {
         : // eslint-disable-next-line @typescript-eslint/no-explicit-any
           (this._protos as any).google.cloud.documentai.v1beta3
             .DocumentProcessorService,
-      this._opts
+      this._opts,
+      this._providedCustomServicePath
     ) as Promise<{[method: string]: Function}>;
 
     // Iterate over each of the methods that the service provides