fix(sources): resolve issue with 'test connection' button on Sources page

frontend/src/pages/SourcesPage.tsx

@@ -433,11 +433,16 @@ const SourcesPage: React.FC = () => {
     try {
       let response;
       if (formData.source_type === 'webdav') {
-        response = await api.post('/webdav/test-connection', {
-          server_url: formData.server_url,
-          username: formData.username,
-          password: formData.password,
-          server_type: formData.server_type,
+        response = await api.post('/sources/test-connection', {
+          source_type: 'webdav',
+          config: {
+            server_url: formData.server_url,
+            username: formData.username,
+            password: formData.password,
+            server_type: formData.server_type,
+            watch_folders: formData.watch_folders,
+            file_extensions: formData.file_extensions,
+          }
         });
       } else if (formData.source_type === 'local_folder') {
         response = await api.post('/sources/test-connection', {

frontend/src/pages/__tests__/SourcesPage.simple.test.tsx

@@ -0,0 +1,94 @@
+import { describe, it, expect } from 'vitest';
+
+describe('SourcesPage Test Connection Fix', () => {
+  it('Test connection should use unified /sources/test-connection endpoint for all source types', () => {
+    // This test documents the fix for the bug where WebDAV test connection
+    // was failing for existing sources because it was using /webdav/test-connection
+    // endpoint which validated watch_folders existence, but the frontend wasn't
+    // sending the watch_folders that were already configured for the source.
+    
+    // The fix ensures all source types (WebDAV, S3, Local Folder) use the same
+    // /sources/test-connection endpoint and include all necessary configuration
+    // including watch_folders and file_extensions.
+    
+    const testConnectionEndpoint = '/sources/test-connection';
+    
+    // All source types should use the same endpoint
+    expect(testConnectionEndpoint).toBe('/sources/test-connection');
+    
+    // WebDAV payload should include watch_folders
+    const webdavPayload = {
+      source_type: 'webdav',
+      config: {
+        server_url: 'https://example.com',
+        username: 'user',
+        password: 'pass',
+        server_type: 'generic',
+        watch_folders: ['/Documents'],  // This was missing before the fix
+        file_extensions: ['pdf', 'jpg']  // This was missing before the fix
+      }
+    };
+    
+    expect(webdavPayload.config.watch_folders).toBeDefined();
+    expect(webdavPayload.config.watch_folders.length).toBeGreaterThan(0);
+    expect(webdavPayload.config.file_extensions).toBeDefined();
+  });
+
+  it('WebDAV config validation should pass when watch_folders are provided', () => {
+    // The backend WebDAVConfig.validate() method requires at least one watch folder
+    // This test documents that requirement
+    
+    const validConfig = {
+      server_url: 'https://webdav.example.com',
+      username: 'testuser',
+      password: 'testpass',
+      watch_folders: ['/Documents'],
+      file_extensions: ['pdf']
+    };
+    
+    const invalidConfig = {
+      server_url: 'https://webdav.example.com',
+      username: 'testuser', 
+      password: 'testpass',
+      watch_folders: [],  // Empty array would fail validation
+      file_extensions: ['pdf']
+    };
+    
+    // Valid config should have at least one watch folder
+    expect(validConfig.watch_folders.length).toBeGreaterThan(0);
+    
+    // Invalid config would fail with "At least one watch folder must be specified"
+    expect(invalidConfig.watch_folders.length).toBe(0);
+  });
+
+  it('Frontend form should preserve watch_folders when editing existing sources', () => {
+    // When editing an existing source, the form should populate with existing config
+    // including watch_folders and file_extensions
+    
+    const existingSourceConfig = {
+      server_url: 'https://existing.webdav.com',
+      username: 'existing',
+      password: 'pass',
+      server_type: 'nextcloud',
+      watch_folders: ['/Documents', '/Photos'],
+      file_extensions: ['pdf', 'jpg', 'png']
+    };
+    
+    // Form data should be populated from existing source
+    const formData = {
+      name: 'Existing Source',
+      source_type: 'webdav',
+      enabled: true,
+      server_url: existingSourceConfig.server_url,
+      username: existingSourceConfig.username,
+      password: existingSourceConfig.password,
+      server_type: existingSourceConfig.server_type,
+      watch_folders: existingSourceConfig.watch_folders,
+      file_extensions: existingSourceConfig.file_extensions
+    };
+    
+    // Verify watch_folders are preserved
+    expect(formData.watch_folders).toEqual(existingSourceConfig.watch_folders);
+    expect(formData.file_extensions).toEqual(existingSourceConfig.file_extensions);
+  });
+});