add test for selectClientAuthMethod

Author: chipgpt

src/client/auth.test.ts

@@ -10,7 +10,8 @@ import {
     discoverOAuthProtectedResourceMetadata,
     extractResourceMetadataUrl,
     auth,
-    type OAuthClientProvider
+    type OAuthClientProvider,
+    selectClientAuthMethod
 } from './auth.js';
 import { ServerError } from '../server/auth/errors.js';
 import { AuthorizationServerMetadata } from '../shared/auth.js';
@@ -881,6 +882,21 @@ describe('OAuth Authorization', () => {
         });
     });
 
+    describe('selectClientAuthMethod', () => {
+        it('selects the correct client authentication method from client information', () => {
+            const clientInfo = { client_id: 'test-client-id', client_secret: 'test-client-secret', token_endpoint_auth_method: 'client_secret_basic' };
+            const supportedMethods = ['client_secret_post', 'client_secret_basic', 'none'];
+            const authMethod = selectClientAuthMethod(clientInfo, supportedMethods);
+            expect(authMethod).toBe('client_secret_basic');
+        });
+        it('selects the correct client authentication method from supported methods', () => {
+            const clientInfo = { client_id: 'test-client-id' };
+            const supportedMethods = ['client_secret_post', 'client_secret_basic', 'none'];
+            const authMethod = selectClientAuthMethod(clientInfo, supportedMethods);
+            expect(authMethod).toBe('none');
+        });
+    });
+
     describe('startAuthorization', () => {
         const validMetadata = {
             issuer: 'https://auth.example.com',

src/client/auth.ts

@@ -169,7 +169,7 @@ const AUTHORIZATION_CODE_CHALLENGE_METHOD = 'S256';
  * @param supportedMethods - Authentication methods supported by the authorization server
  * @returns The selected authentication method
  */
-function selectClientAuthMethod(clientInformation: OAuthClientInformationMixed, supportedMethods: string[]): ClientAuthMethod {
+export function selectClientAuthMethod(clientInformation: OAuthClientInformationMixed, supportedMethods: string[]): ClientAuthMethod {
     const hasClientSecret = clientInformation.client_secret !== undefined;
 
     // If server doesn't specify supported methods, use RFC 6749 defaults