diff --git a/forms-bridge/addons/zoho/class-zoho-form-bridge.php b/forms-bridge/addons/zoho/class-zoho-form-bridge.php
index 3c73a491..9a6c72d7 100644
--- a/forms-bridge/addons/zoho/class-zoho-form-bridge.php
+++ b/forms-bridge/addons/zoho/class-zoho-form-bridge.php
@@ -70,7 +70,16 @@ function ( $headers, $backend ) {
 			2
 		);
 
-		$response = $this->backend()->$method(
+		$backend = $this->backend();
+
+		if ( ! $backend ) {
+			return new WP_Error(
+				'invalid_backend',
+				'The bridge does not have a valid backend'
+			);
+		}
+
+		$response = $backend->$method(
 			$this->endpoint,
 			$payload,
 			array(),
diff --git a/tests/addons/test-bigin.php b/tests/addons/test-bigin.php
index 403b8410..d7efe390 100644
--- a/tests/addons/test-bigin.php
+++ b/tests/addons/test-bigin.php
@@ -6,9 +6,601 @@
  */
 
 use FORMS_BRIDGE\Bigin_Form_Bridge;
+use FORMS_BRIDGE\Bigin_Addon;
+use FORMS_BRIDGE\Addon;
+use HTTP_BRIDGE\Backend;
+use HTTP_BRIDGE\Credential;
 
 /**
- * Bigin test case.
+ * Bigin addon test case.
  */
 class BiginTest extends WP_UnitTestCase {
+
+	/**
+	 * Handles the last intercepted http request data.
+	 *
+	 * @var array
+	 */
+	private static $request;
+
+	/**
+	 * Handles the mock response to return.
+	 *
+	 * @var array|null
+	 */
+	private static $mock_response;
+
+	/**
+	 * Holds the mocked backend name.
+	 *
+	 * @var string
+	 */
+	private const BACKEND_NAME = 'test-bigin-backend';
+
+	/**
+	 * Holds the mocked backend base URL.
+	 *
+	 * @var string
+	 */
+	private const BACKEND_URL = 'https://www.zohoapis.com';
+
+	/**
+	 * Holds the mocked credential name.
+	 *
+	 * @var string
+	 */
+	private const CREDENTIAL_NAME = 'test-bigin-credential';
+
+	/**
+	 * Holds the mocked bridge name.
+	 *
+	 * @var string
+	 */
+	private const BRIDGE_NAME = 'test-bigin-bridge';
+
+	/**
+	 * Test credential provider.
+	 *
+	 * @return Credential[]
+	 */
+	public static function credentials_provider() {
+		return array(
+			new Credential(
+				array(
+					'name'          => self::CREDENTIAL_NAME,
+					'schema'        => 'Bearer',
+					'client_id'     => 'test-client-id',
+					'client_secret' => 'test-client-secret',
+					'region'        => 'zoho.eu',
+					'access_token'  => 'test-access-token',
+					'refresh_token' => 'test-refresh-token',
+					'expires_at'    => time() + 3600,
+					'scope'         => 'ZohoBigin.modules.ALL,ZohoBigin.settings.modules.READ,ZohoBigin.settings.layouts.READ,ZohoBigin.users.READ',
+					'oauth_url'     => 'https://accounts.{region}/oauth/v2',
+				)
+			),
+		);
+	}
+
+	/**
+	 * Test backend provider.
+	 *
+	 * @return Backend[]
+	 */
+	public static function backends_provider() {
+		return array(
+			new Backend(
+				array(
+					'name'       => self::BACKEND_NAME,
+					'base_url'   => self::BACKEND_URL,
+					'credential' => self::CREDENTIAL_NAME,
+					'headers'    => array(
+						array(
+							'name'  => 'Content-Type',
+							'value' => 'application/json',
+						),
+						array(
+							'name'  => 'Accept',
+							'value' => 'application/json',
+						),
+					),
+				)
+			),
+		);
+	}
+
+	/**
+	 * HTTP requests interceptor.
+	 *
+	 * @param mixed  $pre Initial pre hook value.
+	 * @param array  $args Request arguments.
+	 * @param string $url Request URL.
+	 *
+	 * @return array
+	 */
+	public static function pre_http_request( $pre, $args, $url ) {
+		self::$request = array(
+			'args' => $args,
+			'url'  => $url,
+		);
+
+		$http = array(
+			'code'    => 200,
+			'message' => 'SUCCESS',
+		);
+
+		$method = $args['method'] ?? 'POST';
+
+		// Parse URL to determine the endpoint being called.
+		$parsed_url = wp_parse_url( $url );
+		$path       = $parsed_url['path'] ?? '';
+
+		// Parse the body to determine the method being called.
+		$body = array();
+		if ( ! empty( $args['body'] ) ) {
+			if ( is_string( $args['body'] ) ) {
+				$body = json_decode( $args['body'], true );
+			} else {
+				$body = $args['body'];
+			}
+		}
+
+		// Return appropriate mock response based on endpoint.
+		if ( self::$mock_response ) {
+			$http = self::$mock_response['http'] ?? $http;
+			unset( self::$mock_response['http'] );
+			$response_body = self::$mock_response;
+		} else {
+			$response_body = self::get_mock_response( $method, $path, $body );
+		}
+
+		return array(
+			'response'      => $http,
+			'headers'       => array( 'Content-Type' => 'application/json' ),
+			'cookies'       => array(),
+			'body'          => wp_json_encode( $response_body ),
+			'http_response' => null,
+		);
+	}
+
+	/**
+	 * Get mock response based on API endpoint.
+	 *
+	 * @param string $method HTTP method.
+	 * @param string $path API endpoint path.
+	 * @param array  $body Request body.
+	 *
+	 * @return array Mock response.
+	 */
+	private static function get_mock_response( $method, $path, $body ) {
+		switch ( $path ) {
+			case '/bigin/v2/users':
+				return array(
+					'users' => array(
+						array(
+							'id'        => '123456789',
+							'email'     => 'user@example.com',
+							'full_name' => 'Test User',
+						),
+					),
+				);
+
+			case '/bigin/v2/settings/modules':
+				return array(
+					'modules' => array(
+						array(
+							'api_name' => 'Contacts',
+							'name'     => 'Contacts',
+						),
+						array(
+							'api_name' => 'Leads',
+							'name'     => 'Leads',
+						),
+						array(
+							'api_name' => 'Accounts',
+							'name'     => 'Accounts',
+						),
+						array(
+							'api_name' => 'Deals',
+							'name'     => 'Deals',
+						),
+					),
+				);
+
+			case '/bigin/v2/settings/layouts':
+				return array(
+					'layouts' => array(
+						array(
+							'sections' => array(
+								array(
+									'fields' => array(
+										array(
+											'api_name'  => 'First_Name',
+											'json_type' => 'string',
+										),
+										array(
+											'api_name'  => 'Last_Name',
+											'json_type' => 'string',
+										),
+										array(
+											'api_name'  => 'Email',
+											'json_type' => 'string',
+										),
+										array(
+											'api_name'  => 'Phone',
+											'json_type' => 'string',
+										),
+										array(
+											'api_name'  => 'Amount',
+											'json_type' => 'double',
+										),
+									),
+								),
+							),
+						),
+					),
+				);
+
+			case '/bigin/v2/Contacts':
+				if ( 'POST' === $method ) {
+					return array(
+						'data' => array(
+							array(
+								'code'    => 'SUCCESS',
+								'details' => array( 'id' => '123456789' ),
+								'message' => 'record added',
+								'status'  => 'success',
+							),
+						),
+					);
+				}
+				return array(
+					'data' => array(
+						array(
+							'First_Name' => 'John',
+							'Last_Name'  => 'Doe',
+							'Email'      => 'john.doe@example.com',
+						),
+					),
+				);
+
+			case '/bigin/v2/Deals':
+				if ( 'POST' === $method ) {
+					return array(
+						'data' => array(
+							array(
+								'code'    => 'SUCCESS',
+								'details' => array(
+									'id' => '987654321',
+								),
+								'message' => 'record added',
+								'status'  => 'success',
+							),
+						),
+					);
+				}
+
+				return array(
+					'data' => array(
+						array(
+							'Deal_Name' => 'Test Deal',
+							'Amount'    => 1000.00,
+						),
+					),
+				);
+
+			default:
+				return array();
+		}
+	}
+
+	/**
+	 * Set up test fixtures.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		self::$request       = null;
+		self::$mock_response = null;
+
+		tests_add_filter( 'http_bridge_credentials', array( self::class, 'credentials_provider' ), 10, 0 );
+		tests_add_filter( 'http_bridge_backends', array( self::class, 'backends_provider' ), 10, 0 );
+		tests_add_filter( 'pre_http_request', array( self::class, 'pre_http_request' ), 10, 3 );
+	}
+
+	/**
+	 * Tear down test filters.
+	 */
+	public function tear_down() {
+		remove_filter( 'http_bridge_credentials', array( self::class, 'credentials_provider' ), 10, 0 );
+		remove_filter( 'http_bridge_backends', array( self::class, 'backends_provider' ), 10, 0 );
+		remove_filter( 'pre_http_request', array( self::class, 'pre_http_request' ), 10, 3 );
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Test that the addon class exists and has correct constants.
+	 */
+	public function test_addon_class_exists() {
+		$this->assertTrue( class_exists( 'FORMS_BRIDGE\Bigin_Addon' ) );
+		$this->assertEquals( 'Bigin', Bigin_Addon::TITLE );
+		$this->assertEquals( 'bigin', Bigin_Addon::NAME );
+		$this->assertEquals( '\FORMS_BRIDGE\Bigin_Form_Bridge', Bigin_Addon::BRIDGE );
+	}
+
+	/**
+	 * Test that the form bridge class exists.
+	 */
+	public function test_form_bridge_class_exists() {
+		$this->assertTrue( class_exists( 'FORMS_BRIDGE\Bigin_Form_Bridge' ) );
+	}
+
+	/**
+	 * Test bridge validation with valid data.
+	 */
+	public function test_bridge_validation() {
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/bigin/v2/Contacts',
+				'method'   => 'POST',
+			),
+		);
+
+		$this->assertTrue( $bridge->is_valid );
+	}
+
+	/**
+	 * Test bridge validation with invalid data.
+	 */
+	public function test_bridge_validation_invalid() {
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name' => 'invalid-bridge',
+				// Missing required fields.
+			),
+		);
+
+		$this->assertFalse( $bridge->is_valid );
+	}
+
+	/**
+	 * Test POST request to create a contact.
+	 */
+	public function test_post_create_contact() {
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/bigin/v2/Contacts',
+				'method'   => 'POST',
+			),
+			'bigin'
+		);
+
+		$payload = array(
+			'data' => array(
+				array(
+					'First_Name' => 'John',
+					'Last_Name'  => 'Doe',
+					'Email'      => 'john.doe@example.com',
+				),
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertEquals( 'SUCCESS', $response['data']['data'][0]['code'] );
+		$this->assertEquals( 'record added', $response['data']['data'][0]['message'] );
+	}
+
+	/**
+	 * Test POST request to create a deal.
+	 */
+	public function test_post_create_deal() {
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/bigin/v2/Deals',
+				'method'   => 'POST',
+			),
+			'bigin'
+		);
+
+		$payload = array(
+			'data' => array(
+				array(
+					'Deal_Name' => 'Test Deal',
+					'Amount'    => 1000.00,
+				),
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertEquals( 'SUCCESS', $response['data']['data'][0]['code'] );
+		$this->assertEquals( 'record added', $response['data']['data'][0]['message'] );
+	}
+
+	/**
+	 * Test GET request to fetch contacts.
+	 */
+	public function test_get_contacts() {
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/bigin/v2/Contacts',
+				'method'   => 'GET',
+			),
+			'bigin'
+		);
+
+		$response = $bridge->submit();
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertArrayHasKey( 'First_Name', $response['data']['data'][0] );
+		$this->assertEquals( 'John', $response['data']['data'][0]['First_Name'] );
+	}
+
+	/**
+	 * Test addon ping method.
+	 */
+	public function test_addon_ping() {
+		$addon  = Addon::addon( 'bigin' );
+		$result = $addon->ping( self::BACKEND_NAME );
+
+		$this->assertTrue( $result );
+	}
+
+	/**
+	 * Test addon get_endpoints method.
+	 */
+	public function test_addon_get_endpoints() {
+		$addon     = Addon::addon( 'bigin' );
+		$endpoints = $addon->get_endpoints( self::BACKEND_NAME );
+
+		$this->assertIsArray( $endpoints );
+		$this->assertContains( '/bigin/v2/Contacts', $endpoints );
+		$this->assertContains( '/bigin/v2/Leads', $endpoints );
+		$this->assertContains( '/bigin/v2/Accounts', $endpoints );
+		$this->assertContains( '/bigin/v2/Deals', $endpoints );
+	}
+
+	/**
+	 * Test addon get_endpoint_schema method.
+	 */
+	public function test_addon_get_endpoint_schema() {
+		$addon  = Addon::addon( 'bigin' );
+		$schema = $addon->get_endpoint_schema(
+			'/bigin/v2/Contacts',
+			self::BACKEND_NAME,
+			'POST'
+		);
+
+		$this->assertIsArray( $schema );
+		$this->assertNotEmpty( $schema );
+
+		$field_names = array_column( $schema, 'name' );
+		$this->assertContains( 'First_Name', $field_names );
+		$this->assertContains( 'Last_Name', $field_names );
+		$this->assertContains( 'Email', $field_names );
+		$this->assertContains( 'Phone', $field_names );
+		$this->assertContains( 'Amount', $field_names );
+	}
+
+	/**
+	 * Test error response handling.
+	 */
+	public function test_error_response_handling() {
+		self::$mock_response = array(
+			'http'    => array(
+				'code'    => 401,
+				'message' => 'UNAUTHORIZED',
+			),
+			'code'    => 'INVALID_TOKEN',
+			'message' => 'Invalid authentication token',
+		);
+
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/bigin/v2/Contacts',
+				'method'   => 'POST',
+			),
+		);
+
+		$response = $bridge->submit( array() );
+
+		$this->assertTrue( is_wp_error( $response ) );
+	}
+
+	/**
+	 * Test invalid backend handling.
+	 */
+	public function test_invalid_backend() {
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name'     => 'test-invalid-backend-bridge',
+				'backend'  => 'non-existent-backend',
+				'endpoint' => '/bigin/v2/Contacts',
+				'method'   => 'POST',
+			),
+		);
+
+		$response = $bridge->submit( array() );
+
+		$this->assertTrue( is_wp_error( $response ) );
+		$this->assertEquals( 'invalid_backend', $response->get_error_code() );
+	}
+
+	/**
+	 * Test duplicate data handling.
+	 */
+	public function test_duplicate_data_handling() {
+		self::$mock_response = array(
+			'data' => array(
+				array(
+					'code'    => 'DUPLICATE_DATA',
+					'message' => 'Duplicate record found',
+				),
+			),
+		);
+
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/bigin/v2/Contacts',
+				'method'   => 'POST',
+			),
+		);
+
+		$response = $bridge->submit(
+			array(
+				'data' => array(
+					array(
+						'Email' => 'duplicate@example.com',
+					),
+				),
+			)
+		);
+
+		// Should not return WP_Error for DUPLICATE_DATA
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
+
+	/**
+	 * Test authorization header transformation.
+	 */
+	public function test_authorization_header_transformation() {
+		$bridge = new Bigin_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/bigin/v2/Contacts',
+				'method'   => 'GET',
+			),
+		);
+
+		$bridge->submit();
+
+		// Check that the request was made
+		$this->assertNotNull( self::$request );
+
+		// Verify the Authorization header was transformed
+		$headers = self::$request['args']['headers'] ?? array();
+		$this->assertArrayHasKey( 'Authorization', $headers );
+		$this->assertStringContainsString( 'Zoho-oauthtoken', $headers['Authorization'] );
+	}
 }
diff --git a/tests/addons/test-rocketchat.php b/tests/addons/test-rocketchat.php
new file mode 100644
index 00000000..220a796d
--- /dev/null
+++ b/tests/addons/test-rocketchat.php
@@ -0,0 +1,14 @@
+<?php
+/**
+ * Class RocketchatTest
+ *
+ * @package formsbridge-tests
+ */
+
+use FORMS_BRIDGE\Rocketchat_Form_Bridge;
+
+/**
+ * Rocketchat test case.
+ */
+class RocketchatTest extends WP_UnitTestCase {
+}
diff --git a/tests/addons/test-slack.php b/tests/addons/test-slack.php
new file mode 100644
index 00000000..5c52b549
--- /dev/null
+++ b/tests/addons/test-slack.php
@@ -0,0 +1,14 @@
+<?php
+/**
+ * Class SlackTest
+ *
+ * @package formsbridge-tests
+ */
+
+use FORMS_BRIDGE\Slack_Form_Bridge;
+
+/**
+ * Slack test case.
+ */
+class SlackTest extends WP_UnitTestCase {
+}
diff --git a/tests/addons/test-zoho.php b/tests/addons/test-zoho.php
index ea6887fd..3060d700 100644
--- a/tests/addons/test-zoho.php
+++ b/tests/addons/test-zoho.php
@@ -6,9 +6,602 @@
  */
 
 use FORMS_BRIDGE\Zoho_Form_Bridge;
+use FORMS_BRIDGE\Zoho_Addon;
+use FORMS_BRIDGE\Addon;
+use HTTP_BRIDGE\Backend;
+use HTTP_BRIDGE\Credential;
 
 /**
- * Zoho test case.
+ * Zoho addon test case.
  */
 class ZohoTest extends WP_UnitTestCase {
+
+	/**
+	 * Handles the last intercepted http request data.
+	 *
+	 * @var array
+	 */
+	private static $request;
+
+	/**
+	 * Handles the mock response to return.
+	 *
+	 * @var array|null
+	 */
+	private static $mock_response;
+
+	/**
+	 * Holds the mocked backend name.
+	 *
+	 * @var string
+	 */
+	private const BACKEND_NAME = 'test-zoho-backend';
+
+	/**
+	 * Holds the mocked backend base URL.
+	 *
+	 * @var string
+	 */
+	private const BACKEND_URL = 'https://www.zohoapis.com';
+
+	/**
+	 * Holds the mocked credential name.
+	 *
+	 * @var string
+	 */
+	private const CREDENTIAL_NAME = 'test-zoho-credential';
+
+	/**
+	 * Holds the mocked bridge name.
+	 *
+	 * @var string
+	 */
+	private const BRIDGE_NAME = 'test-zoho-bridge';
+
+	/**
+	 * Test credential provider.
+	 *
+	 * @return Credential[]
+	 */
+	public static function credentials_provider() {
+		return array(
+			new Credential(
+				array(
+					'name'          => self::CREDENTIAL_NAME,
+					'schema'        => 'Bearer',
+					'client_id'     => 'test-client-id',
+					'client_secret' => 'test-client-secret',
+					'region'        => 'zoho.eu',
+					'access_token'  => 'test-access-token',
+					'refresh_token' => 'test-refresh-token',
+					'expires_at'    => time() + 3600,
+					'scope'         => 'ZohoCRM.modules.ALL,ZohoCRM.settings.modules.READ,ZohoCRM.settings.layouts.READ,ZohoCRM.users.READ',
+					'oauth_url'     => 'https://accounts.{region}/oauth/v2',
+				)
+			),
+		);
+	}
+
+	/**
+	 * Test backend provider.
+	 *
+	 * @return Backend[]
+	 */
+	public static function backends_provider() {
+		return array(
+			new Backend(
+				array(
+					'name'       => self::BACKEND_NAME,
+					'base_url'   => self::BACKEND_URL,
+					'credential' => self::CREDENTIAL_NAME,
+					'headers'    => array(
+						array(
+							'name'  => 'Content-Type',
+							'value' => 'application/json',
+						),
+						array(
+							'name'  => 'Accept',
+							'value' => 'application/json',
+						),
+					),
+				)
+			),
+		);
+	}
+
+	/**
+	 * HTTP requests interceptor.
+	 *
+	 * @param mixed  $pre Initial pre hook value.
+	 * @param array  $args Request arguments.
+	 * @param string $url Request URL.
+	 *
+	 * @return array
+	 */
+	public static function pre_http_request( $pre, $args, $url ) {
+		self::$request = array(
+			'args' => $args,
+			'url'  => $url,
+		);
+
+		$http = array(
+			'code'    => 200,
+			'message' => 'SUCCESS',
+		);
+
+		$method = $args['method'] ?? 'POST';
+
+		// Parse URL to determine the endpoint being called.
+		$parsed_url = wp_parse_url( $url );
+		$path       = $parsed_url['path'] ?? '';
+
+		// Parse the body to determine the method being called.
+		$body = array();
+		if ( ! empty( $args['body'] ) ) {
+			if ( is_string( $args['body'] ) ) {
+				$body = json_decode( $args['body'], true );
+			} else {
+				$body = $args['body'];
+			}
+		}
+
+		// Return appropriate mock response based on endpoint.
+		if ( self::$mock_response ) {
+			$http = self::$mock_response['http'] ?? $http;
+			unset( self::$mock_response['http'] );
+			$response_body = self::$mock_response;
+		} else {
+			$response_body = self::get_mock_response( $method, $path, $body );
+		}
+
+		return array(
+			'response'      => $http,
+			'headers'       => array( 'Content-Type' => 'application/json' ),
+			'cookies'       => array(),
+			'body'          => wp_json_encode( $response_body ),
+			'http_response' => null,
+		);
+	}
+
+	/**
+	 * Get mock response based on API endpoint.
+	 *
+	 * @param string $method HTTP method.
+	 * @param string $path API endpoint path.
+	 * @param array  $body Request body.
+	 *
+	 * @return array Mock response.
+	 */
+	private static function get_mock_response( $method, $path, $body ) {
+		switch ( $path ) {
+			case '/crm/v7/users':
+				return array(
+					'users' => array(
+						array(
+							'id'        => '123456789',
+							'email'     => 'user@example.com',
+							'full_name' => 'Test User',
+						),
+					),
+				);
+
+			case '/crm/v7/settings/modules':
+				return array(
+					'modules' => array(
+						array(
+							'api_name' => 'Contacts',
+							'name'     => 'Contacts',
+						),
+						array(
+							'api_name' => 'Leads',
+							'name'     => 'Leads',
+						),
+						array(
+							'api_name' => 'Accounts',
+							'name'     => 'Accounts',
+						),
+						array(
+							'api_name' => 'Deals',
+							'name'     => 'Deals',
+						),
+					),
+				);
+
+			case '/crm/v7/settings/layouts':
+				return array(
+					'layouts' => array(
+						array(
+							'sections' => array(
+								array(
+									'fields' => array(
+										array(
+											'api_name'  => 'First_Name',
+											'json_type' => 'string',
+										),
+										array(
+											'api_name'  => 'Last_Name',
+											'json_type' => 'string',
+										),
+										array(
+											'api_name'  => 'Email',
+											'json_type' => 'string',
+										),
+										array(
+											'api_name'  => 'Phone',
+											'json_type' => 'string',
+										),
+										array(
+											'api_name'  => 'Amount',
+											'json_type' => 'double',
+										),
+									),
+								),
+							),
+						),
+					),
+				);
+
+			case '/crm/v7/Contacts':
+				if ( 'POST' === $method ) {
+					return array(
+						'data' => array(
+							array(
+								'code'    => 'SUCCESS',
+								'details' => array(
+									'id' => '123456789',
+								),
+								'message' => 'record added',
+								'status'  => 'success',
+							),
+						),
+					);
+				}
+				return array(
+					'data' => array(
+						array(
+							'First_Name' => 'John',
+							'Last_Name'  => 'Doe',
+							'Email'      => 'john.doe@example.com',
+						),
+					),
+				);
+
+			case '/crm/v7/Deals':
+				if ( 'POST' === $method ) {
+					return array(
+						'data' => array(
+							array(
+								'code'    => 'SUCCESS',
+								'details' => array( 'id' => '987654321' ),
+								'message' => 'record added',
+								'status'  => 'success',
+							),
+						),
+					);
+				}
+				return array(
+					'data' => array(
+						array(
+							'Deal_Name' => 'Test Deal',
+							'Amount'    => 1000.00,
+						),
+					),
+				);
+
+			default:
+				return array();
+		}
+	}
+
+	/**
+	 * Set up test fixtures.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		self::$request       = null;
+		self::$mock_response = null;
+
+		tests_add_filter( 'http_bridge_credentials', array( self::class, 'credentials_provider' ), 10, 0 );
+		tests_add_filter( 'http_bridge_backends', array( self::class, 'backends_provider' ), 10, 0 );
+		tests_add_filter( 'pre_http_request', array( self::class, 'pre_http_request' ), 10, 3 );
+	}
+
+	/**
+	 * Tear down test filters.
+	 */
+	public function tear_down() {
+		remove_filter( 'http_bridge_credentials', array( self::class, 'credentials_provider' ), 10, 0 );
+		remove_filter( 'http_bridge_backends', array( self::class, 'backends_provider' ), 10, 0 );
+		remove_filter( 'pre_http_request', array( self::class, 'pre_http_request' ), 10, 3 );
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Test that the addon class exists and has correct constants.
+	 */
+	public function test_addon_class_exists() {
+		$this->assertTrue( class_exists( 'FORMS_BRIDGE\Zoho_Addon' ) );
+		$this->assertEquals( 'Zoho', Zoho_Addon::TITLE );
+		$this->assertEquals( 'zoho', Zoho_Addon::NAME );
+		$this->assertEquals( '\FORMS_BRIDGE\Zoho_Form_Bridge', Zoho_Addon::BRIDGE );
+	}
+
+	/**
+	 * Test that the form bridge class exists.
+	 */
+	public function test_form_bridge_class_exists() {
+		$this->assertTrue( class_exists( 'FORMS_BRIDGE\Zoho_Form_Bridge' ) );
+	}
+
+	/**
+	 * Test bridge validation with valid data.
+	 */
+	public function test_bridge_validation() {
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/crm/v7/Contacts',
+				'method'   => 'POST',
+			),
+			'zoho'
+		);
+
+		$this->assertTrue( $bridge->is_valid );
+	}
+
+	/**
+	 * Test bridge validation with invalid data.
+	 */
+	public function test_bridge_validation_invalid() {
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name' => 'invalid-bridge',
+				// Missing required fields.
+			),
+			'zoho'
+		);
+
+		$this->assertFalse( $bridge->is_valid );
+	}
+
+	/**
+	 * Test POST request to create a contact.
+	 */
+	public function test_post_create_contact() {
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/crm/v7/Contacts',
+				'method'   => 'POST',
+			),
+			'zoho'
+		);
+
+		$payload = array(
+			'data' => array(
+				array(
+					'First_Name' => 'John',
+					'Last_Name'  => 'Doe',
+					'Email'      => 'john.doe@example.com',
+				),
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertEquals( 'SUCCESS', $response['data']['data'][0]['code'] );
+		$this->assertEquals( 'record added', $response['data']['data'][0]['message'] );
+	}
+
+	/**
+	 * Test POST request to create a deal.
+	 */
+	public function test_post_create_deal() {
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/crm/v7/Deals',
+				'method'   => 'POST',
+			),
+			'zoho'
+		);
+
+		$payload = array(
+			'data' => array(
+				array(
+					'Deal_Name' => 'Test Deal',
+					'Amount'    => 1000.00,
+				),
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertEquals( 'SUCCESS', $response['data']['data'][0]['code'] );
+		$this->assertEquals( 'record added', $response['data']['data'][0]['message'] );
+	}
+
+	/**
+	 * Test GET request to fetch contacts.
+	 */
+	public function test_get_contacts() {
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/crm/v7/Contacts',
+				'method'   => 'GET',
+			),
+			'zoho'
+		);
+
+		$response = $bridge->submit();
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertArrayHasKey( 'First_Name', $response['data']['data'][0] );
+		$this->assertEquals( 'John', $response['data']['data'][0]['First_Name'] );
+	}
+
+	/**
+	 * Test addon ping method.
+	 */
+	public function test_addon_ping() {
+		$addon    = Addon::addon( 'zoho' );
+		$response = $addon->ping( self::BACKEND_NAME );
+
+		$this->assertTrue( $response );
+	}
+
+	/**
+	 * Test addon get_endpoints method.
+	 */
+	public function test_addon_get_endpoints() {
+		$addon     = Addon::addon( 'zoho' );
+		$endpoints = $addon->get_endpoints( self::BACKEND_NAME );
+
+		$this->assertIsArray( $endpoints );
+		$this->assertContains( '/crm/v7/Contacts', $endpoints );
+		$this->assertContains( '/crm/v7/Leads', $endpoints );
+		$this->assertContains( '/crm/v7/Accounts', $endpoints );
+		$this->assertContains( '/crm/v7/Deals', $endpoints );
+	}
+
+	/**
+	 * Test addon get_endpoint_schema method.
+	 */
+	public function test_addon_get_endpoint_schema() {
+		$addon  = Addon::addon( 'zoho' );
+		$schema = $addon->get_endpoint_schema(
+			'/crm/v7/Contacts',
+			self::BACKEND_NAME,
+			'POST'
+		);
+
+		$this->assertIsArray( $schema );
+		$this->assertNotEmpty( $schema );
+
+		$field_names = array_column( $schema, 'name' );
+		$this->assertContains( 'First_Name', $field_names );
+		$this->assertContains( 'Last_Name', $field_names );
+		$this->assertContains( 'Email', $field_names );
+		$this->assertContains( 'Phone', $field_names );
+		$this->assertContains( 'Amount', $field_names );
+	}
+
+	/**
+	 * Test error response handling.
+	 */
+	public function test_error_response_handling() {
+		self::$mock_response = array(
+			'http'    => array(
+				'code'    => 401,
+				'message' => 'UNAUTHORIZED',
+			),
+			'code'    => 'INVALID_TOKEN',
+			'message' => 'Invalid authentication token',
+		);
+
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/crm/v7/Contacts',
+				'method'   => 'POST',
+			),
+		);
+
+		$response = $bridge->submit( array() );
+
+		$this->assertTrue( is_wp_error( $response ) );
+	}
+
+	/**
+	 * Test invalid backend handling.
+	 */
+	public function test_invalid_backend() {
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name'     => 'test-invalid-backend-bridge',
+				'backend'  => 'non-existent-backend',
+				'endpoint' => '/crm/v7/Contacts',
+				'method'   => 'POST',
+			),
+		);
+
+		$response = $bridge->submit( array() );
+
+		$this->assertTrue( is_wp_error( $response ) );
+		$this->assertEquals( 'invalid_backend', $response->get_error_code() );
+	}
+
+	/**
+	 * Test duplicate data handling.
+	 */
+	public function test_duplicate_data_handling() {
+		self::$mock_response = array(
+			'data' => array(
+				array(
+					'code'    => 'DUPLICATE_DATA',
+					'message' => 'Duplicate record found',
+				),
+			),
+		);
+
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/crm/v7/Contacts',
+				'method'   => 'POST',
+			),
+		);
+
+		$response = $bridge->submit(
+			array(
+				'data' => array(
+					array(
+						'Email' => 'duplicate@example.com',
+					),
+				),
+			)
+		);
+
+		// Should not return WP_Error for DUPLICATE_DATA
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
+
+	/**
+	 * Test authorization header transformation.
+	 */
+	public function test_authorization_header_transformation() {
+		$bridge = new Zoho_Form_Bridge(
+			array(
+				'name'     => self::BRIDGE_NAME,
+				'backend'  => self::BACKEND_NAME,
+				'endpoint' => '/crm/v7/Contacts',
+				'method'   => 'GET',
+			),
+		);
+
+		$bridge->submit();
+
+		// Check that the request was made
+		$this->assertNotNull( self::$request );
+
+		// Verify the Authorization header was transformed
+		$headers = self::$request['args']['headers'] ?? array();
+		$this->assertArrayHasKey( 'Authorization', $headers );
+		$this->assertStringContainsString( 'Zoho-oauthtoken', $headers['Authorization'] );
+	}
 }
diff --git a/tests/addons/test-zulip.php b/tests/addons/test-zulip.php
new file mode 100644
index 00000000..26ddaa6f
--- /dev/null
+++ b/tests/addons/test-zulip.php
@@ -0,0 +1,14 @@
+<?php
+/**
+ * Class ZulipTest
+ *
+ * @package formsbridge-tests
+ */
+
+use FORMS_BRIDGE\Zulip_Form_Bridge;
+
+/**
+ * Zulip test case.
+ */
+class ZulipTest extends WP_UnitTestCase {
+}