diff --git a/README.md b/README.md
index 152ee362..8fe74b2e 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,7 @@ Forms Bridge has the following addons:
 - [Brevo](https://formsbridge.codeccoop.org/documentation/brevo/)
 - [Dolibarr](https://formsbridge.codeccoop.org/documentation/dolibarr/)
 - [FinanCoop](https://formsbridge.codeccoop.org/documentation/financoop/)
+- [Google Calendar](https://formsbridge.codeccoop.org/documentation/google-calendar/)
 - [Google Sheets](https://formsbridge.codeccoop.org/documentation/google-sheets/)
 - [Holded](https://formsbridge.codeccoop.org/documentation/holded/)
 - [Listmonk](https://formsbridge.codeccoop.org/documentation/listmonk/)
diff --git a/forms-bridge/addons/gcalendar/assets/logo.png b/forms-bridge/addons/gcalendar/assets/logo.png
new file mode 100644
index 00000000..0767b22c
Binary files /dev/null and b/forms-bridge/addons/gcalendar/assets/logo.png differ
diff --git a/forms-bridge/addons/gcalendar/class-gcalendar-addon.php b/forms-bridge/addons/gcalendar/class-gcalendar-addon.php
new file mode 100644
index 00000000..5985589d
--- /dev/null
+++ b/forms-bridge/addons/gcalendar/class-gcalendar-addon.php
@@ -0,0 +1,221 @@
+<?php
+/**
+ * Class GCalendar_Addon
+ *
+ * @package formsbridge
+ */
+
+namespace FORMS_BRIDGE;
+
+use FBAPI;
+use WP_Error;
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit();
+}
+
+require_once 'class-gcalendar-form-bridge.php';
+require_once 'hooks.php';
+
+/**
+ * Google Calendar addon class.
+ */
+class GCalendar_Addon extends Addon {
+
+	/**
+	 * Handles the addon's title.
+	 *
+	 * @var string
+	 */
+	const TITLE = 'Google Calendar';
+
+	/**
+	 * Handles the addon's name.
+	 *
+	 * @var string
+	 */
+	const NAME = 'gcalendar';
+
+	/**
+	 * Handles the addon's custom bridge class.
+	 *
+	 * @var string
+	 */
+	const BRIDGE = '\FORMS_BRIDGE\GCalendar_Form_Bridge';
+
+	/**
+	 * Performs a request against the backend to check the connexion status.
+	 *
+	 * @param string $backend Backend name.
+	 *
+	 * @return boolean
+	 */
+	public function ping( $backend ) {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => '__gcalendar-' . time(),
+				'backend'  => $backend,
+				'endpoint' => '/calendar/v3/users/me/calendarList',
+				'method'   => 'GET',
+			)
+		);
+
+		$backend = $bridge->backend;
+		if ( ! $backend ) {
+			Logger::log( 'Google Calendar backend ping error: Bridge has no valid backend', Logger::ERROR );
+			return false;
+		}
+
+		$credential = $backend->credential;
+		if ( ! $credential ) {
+			Logger::log( 'Google Calendar backend ping error: Backend has no valid credential', Logger::ERROR );
+			return false;
+		}
+
+		$parsed = wp_parse_url( $backend->base_url );
+		$host   = $parsed['host'] ?? '';
+
+		if ( 'www.googleapis.com' !== $host ) {
+			Logger::log( 'Google Calendar backend ping error: Backend does not point to the Google Calendar API endpoints', Logger::ERROR );
+			return false;
+		}
+
+		$access_token = $credential->get_access_token();
+
+		if ( ! $access_token ) {
+			Logger::log( 'Google Calendar backend ping error: Unable to recover the credential access token', Logger::ERROR );
+			return false;
+		}
+
+		return true;
+	}
+
+	/**
+	 * Performs a GET request against the backend endpoint and retrieve the response data.
+	 *
+	 * @param string $endpoint Calendar ID or endpoint.
+	 * @param string $backend Backend name.
+	 *
+	 * @return array|WP_Error
+	 */
+	public function fetch( $endpoint, $backend ) {
+		$backend = FBAPI::get_backend( $backend );
+		if ( ! $backend ) {
+			return new WP_Error( 'invalid_backend' );
+		}
+
+		$credential = $backend->credential;
+		if ( ! $credential ) {
+			return new WP_Error( 'invalid_credential' );
+		}
+
+		$access_token = $credential->get_access_token();
+		if ( ! $access_token ) {
+			return new WP_Error( 'invalid_credential' );
+		}
+
+		$response = http_bridge_get(
+			'https://www.googleapis.com/calendar/v3/users/me/calendarList',
+			array(),
+			array(
+				'Authorization' => "Bearer {$access_token}",
+				'Accept'        => 'application/json',
+			)
+		);
+
+		if ( is_wp_error( $response ) ) {
+			return $response;
+		}
+
+		return $response;
+	}
+
+	/**
+	 * Performs an introspection of the backend endpoint and returns API fields
+	 * and accepted content type.
+	 *
+	 * @param string      $endpoint Calendar ID.
+	 * @param string      $backend Backend name.
+	 * @param string|null $method HTTP method.
+	 *
+	 * @return array List of fields and content type of the endpoint.
+	 */
+	public function get_endpoint_schema( $endpoint, $backend, $method = null ) {
+		if ( ! in_array( $method, array( 'POST', 'PUT' ), true ) ) {
+			return array();
+		}
+
+		return array(
+			array(
+				'name'   => 'summary',
+				'schema' => array(
+					'type'        => 'string',
+					'description' => 'Event title',
+				),
+			),
+			array(
+				'name'   => 'description',
+				'schema' => array(
+					'type'        => 'string',
+					'description' => 'Event description',
+				),
+			),
+			array(
+				'name'   => 'location',
+				'schema' => array(
+					'type'        => 'string',
+					'description' => 'Event location',
+				),
+			),
+			array(
+				'name'   => 'start',
+				'schema' => array(
+					'type'                 => 'object',
+					'properties'           => array(
+						'dateTime' => array(
+							'type'        => 'string',
+							'description' => 'Start date and time (ISO 8601 format)',
+						),
+						'timeZone' => array(
+							'type'        => 'string',
+							'description' => 'Start timezone',
+						),
+					),
+					'additionalProperties' => false,
+					'required'             => array( 'dateTime' ),
+				),
+			),
+			array(
+				'name'   => 'end',
+				'schema' => array(
+					'type'                 => 'object',
+					'properties'           => array(
+						'dateTime' => array(
+							'type'        => 'string',
+							'description' => 'End date and time (ISO 8601 format)',
+						),
+						'timeZone' => array(
+							'type'        => 'string',
+							'description' => 'End timezone',
+						),
+					),
+					'additionalProperties' => false,
+					'required'             => array( 'dateTime' ),
+				),
+			),
+			array(
+				'name'   => 'attendees',
+				'schema' => array(
+					'type'            => 'array',
+					'items'           => array(
+						'type'        => 'string',
+						'description' => 'attendee email address',
+					),
+					'additionalItems' => true,
+				),
+			),
+		);
+	}
+}
+
+GCalendar_Addon::setup();
diff --git a/forms-bridge/addons/gcalendar/class-gcalendar-form-bridge.php b/forms-bridge/addons/gcalendar/class-gcalendar-form-bridge.php
new file mode 100644
index 00000000..d09b0d19
--- /dev/null
+++ b/forms-bridge/addons/gcalendar/class-gcalendar-form-bridge.php
@@ -0,0 +1,190 @@
+<?php
+/**
+ * Class GCalendar_Form_Bridge
+ *
+ * @package formsbridge
+ */
+
+namespace FORMS_BRIDGE;
+
+use WP_Error;
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit();
+}
+
+/**
+ * Form bridge implementation for the Google Calendar service.
+ */
+class GCalendar_Form_Bridge extends Form_Bridge {
+
+	/**
+	 * Bridge constructor with addon name provisioning.
+	 *
+	 * @param array $data Bridge data.
+	 */
+	public function __construct( $data ) {
+		parent::__construct( $data, 'gcalendar' );
+	}
+
+	/**
+	 * Sends the payload to the backend to create a calendar event.
+	 *
+	 * @param array $payload Submission data.
+	 * @param array $attachments Submission's attached files. Will be ignored.
+	 *
+	 * @return array|WP_Error Http request response.
+	 */
+	public function submit( $payload = array(), $attachments = array() ) {
+		if ( ! $this->is_valid ) {
+			return new WP_Error(
+				'invalid_bridge',
+				'Bridge data is invalid',
+				(array) $this->data,
+			);
+		}
+
+		$backend = $this->backend;
+		if ( ! $backend ) {
+			return new WP_Error( 'invalid_backend', 'Backend not found' );
+		}
+
+		$event = $this->transform_to_event( $payload );
+
+		if ( is_wp_error( $event ) ) {
+			return $event;
+		}
+
+		$endpoint = $this->endpoint;
+		$method   = $this->method;
+
+		return $this->backend->$method( $endpoint, $event );
+	}
+
+	/**
+	 * Transforms the form payload into a Google Calendar event structure.
+	 *
+	 * @param array $payload Form submission payload.
+	 *
+	 * @return array|WP_Error Calendar event data.
+	 */
+	private function transform_to_event( $payload ) {
+		$event = array();
+
+		if ( isset( $payload['summary'] ) ) {
+			$event['summary'] = $payload['summary'];
+		}
+
+		if ( isset( $payload['description'] ) ) {
+			$event['description'] = $payload['description'];
+		}
+
+		if ( isset( $payload['location'] ) ) {
+			$event['location'] = $payload['location'];
+		}
+
+		if ( isset( $payload['start'] ) ) {
+			$event['start'] = $this->parse_datetime( $payload['start'] );
+		}
+
+		if ( isset( $payload['end'] ) ) {
+			$event['end'] = $this->parse_datetime( $payload['end'] );
+		}
+
+		if ( ! isset( $event['end'] ) && isset( $event['start']['dateTime'] ) ) {
+			$start_time   = strtotime( $event['start']['dateTime'] );
+			$end_time     = $start_time + 3600;
+			$event['end'] = array(
+				'dateTime' => gmdate( 'Y-m-d\TH:i:s', $end_time ),
+				'timeZone' => $event['start']['timeZone'],
+			);
+		}
+
+		if ( isset( $payload['attendees'] ) ) {
+			$attendees = array();
+			if ( is_string( $payload['attendees'] ) ) {
+				$emails = array_map( 'trim', explode( ',', $payload['attendees'] ) );
+				foreach ( $emails as $email ) {
+					if ( is_email( $email ) ) {
+						$attendees[] = array( 'email' => $email );
+					}
+				}
+			} elseif ( is_array( $payload['attendees'] ) ) {
+				foreach ( $payload['attendees'] as $attendee ) {
+					if ( is_string( $attendee ) && is_email( $attendee ) ) {
+						$attendees[] = array( 'email' => $attendee );
+					} elseif ( is_array( $attendee ) && isset( $attendee['email'] ) ) {
+						$attendees[] = $attendee;
+					}
+				}
+			}
+
+			if ( ! empty( $attendees ) ) {
+				$event['attendees'] = $attendees;
+			}
+		}
+
+		if ( isset( $payload['reminders'] ) ) {
+			$event['reminders'] = $payload['reminders'];
+		}
+
+		if ( isset( $payload['colorId'] ) ) {
+			$event['colorId'] = $payload['colorId'];
+		}
+
+		if ( isset( $payload['sendUpdates'] ) ) {
+			$event['sendUpdates'] = (bool) $payload['sendUpdates'];
+		}
+
+		if ( ! ( isset( $event['start'] ) && isset( $event['end'] ) ) ) {
+			return new WP_Error(
+				'missing_event_dates',
+				'Event must have a start and an end date',
+				$payload,
+			);
+		}
+
+		if ( ! isset( $event['summary'] ) ) {
+			return new WP_Error(
+				'missing_summary',
+				'Event must have a summary (title)',
+				$payload
+			);
+		}
+
+		return $event;
+	}
+
+	/**
+	 * Parses a datetime value into Google Calendar format.
+	 *
+	 * @param mixed $datetime DateTime value (timestamp, string, or array).
+	 *
+	 * @return array DateTime structure for Google Calendar.
+	 */
+	private function parse_datetime( $datetime ) {
+		if ( is_array( $datetime ) && isset( $datetime['dateTime'] ) ) {
+			return $datetime;
+		}
+
+		$timezone = wp_timezone_string();
+
+		if ( is_numeric( $datetime ) ) {
+			$dt = gmdate( 'Y-m-d\TH:i:s', $datetime );
+		} elseif ( is_string( $datetime ) ) {
+			$timestamp = strtotime( $datetime );
+			if ( false === $timestamp ) {
+				$dt = gmdate( 'Y-m-d\TH:i:s' );
+			} else {
+				$dt = gmdate( 'Y-m-d\TH:i:s', $timestamp );
+			}
+		} else {
+			$dt = gmdate( 'Y-m-d\TH:i:s' );
+		}
+
+		return array(
+			'dateTime' => $dt,
+			'timeZone' => $timezone,
+		);
+	}
+}
diff --git a/forms-bridge/addons/gcalendar/hooks.php b/forms-bridge/addons/gcalendar/hooks.php
new file mode 100644
index 00000000..55bdf1e1
--- /dev/null
+++ b/forms-bridge/addons/gcalendar/hooks.php
@@ -0,0 +1,211 @@
+<?php
+/**
+ * Google Calendar addon hooks
+ *
+ * @package formsbridge
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit();
+}
+
+add_filter(
+	'forms_bridge_bridge_schema',
+	function ( $schema, $addon ) {
+		if ( 'gcalendar' !== $addon ) {
+			return $schema;
+		}
+
+		$schema['properties']['endpoint']['default'] = '/calendars/v3/calendar/{$calendarId}/events';
+
+		$schema['properties']['backend']['default'] = 'Calendar API';
+
+		$schema['properties']['method']['enum']    = array( 'GET', 'POST', 'PUT', 'PATCH', 'DELETE' );
+		$schema['properties']['method']['default'] = 'POST';
+
+		return $schema;
+	},
+	10,
+	2
+);
+
+add_filter(
+	'forms_bridge_template_defaults',
+	function ( $defaults, $addon, $schema ) {
+		if ( 'gcalendar' !== $addon ) {
+			return $defaults;
+		}
+
+		$defaults = wpct_plugin_merge_object(
+			array(
+				'fields'     => array(
+					array(
+						'ref'      => '#credential',
+						'name'     => 'name',
+						'label'    => __( 'Name', 'forms-bridge' ),
+						'type'     => 'text',
+						'required' => true,
+					),
+					array(
+						'ref'   => '#credential',
+						'name'  => 'schema',
+						'type'  => 'text',
+						'value' => 'Bearer',
+					),
+					array(
+						'ref'   => '#credential',
+						'name'  => 'oauth_url',
+						'label' => __( 'Authorization URL', 'forms-bridge' ),
+						'type'  => 'text',
+						'value' => 'https://accounts.google.com/o/oauth2/v2',
+					),
+					array(
+						'ref'      => '#credential',
+						'name'     => 'client_id',
+						'label'    => __( 'Client ID', 'forms-bridge' ),
+						'type'     => 'text',
+						'required' => true,
+					),
+					array(
+						'ref'      => '#credential',
+						'name'     => 'client_secret',
+						'label'    => __( 'Client secret', 'forms-bridge' ),
+						'type'     => 'text',
+						'required' => true,
+					),
+					array(
+						'ref'      => '#credential',
+						'name'     => 'scope',
+						'label'    => __( 'Scope', 'forms-bridge' ),
+						'type'     => 'text',
+						'value'    => 'https://www.googleapis.com/auth/calendar.readonly https://www.googleapis.com/auth/calendar.events',
+						'required' => true,
+					),
+					array(
+						'ref'      => '#bridge',
+						'name'     => 'endpoint',
+						'label'    => __( 'Calendar', 'forms-bridge' ),
+						'type'     => 'select',
+						'options'  => array(
+							'endpoint' => '/calendar/v3/users/me/calendarList',
+							'finger'   => array(
+								'value' => 'items[].id',
+								'label' => 'items[].summary',
+							),
+						),
+						'required' => true,
+					),
+					array(
+						'ref'   => '#bridge',
+						'name'  => 'method',
+						'value' => 'POST',
+					),
+					array(
+						'ref'      => '#bridge/custom_fields[]',
+						'name'     => 'duration_hours',
+						'label'    => __( 'Duration (Hours)', 'forms-bridge' ),
+						'type'     => 'number',
+						'required' => true,
+						'default'  => 1,
+					),
+					array(
+						'ref'     => '#bridge/custom_fields[]',
+						'name'    => 'duration_minutes',
+						'label'   => __( 'Duration (Minutes)', 'forms-bridge' ),
+						'type'    => 'number',
+						'default' => 0,
+					),
+					array(
+						'ref'         => '#bridge/custom_fields[]',
+						'name'        => 'location',
+						'label'       => __( 'Location', 'forms-bridge' ),
+						'description' => __(
+							'Geographic location of the event as free-form text',
+							'forms-bridge',
+						),
+						'type'        => 'text',
+					),
+					array(
+						'ref'     => '#bridge/custom_fields[]',
+						'name'    => 'sendUpdates',
+						'label'   => __( 'Send email notification', 'forms-bridge' ),
+						'type'    => 'boolean',
+						'default' => true,
+					),
+					array(
+						'ref'     => '#backend',
+						'name'    => 'name',
+						'default' => 'Calendar API',
+					),
+					array(
+						'ref'   => '#backend',
+						'name'  => 'base_url',
+						'value' => 'https://www.googleapis.com',
+					),
+				),
+				'backend'    => array(
+					'name'     => 'Calendar API',
+					'base_url' => 'https://www.googleapis.com',
+					'headers'  => array(
+						array(
+							'name'  => 'Accept',
+							'value' => 'application/json',
+						),
+					),
+				),
+				'bridge'     => array(
+					'backend'  => 'Calendar API',
+					'endpoint' => '/calendar/v3/calendars/{$calendarId}/events',
+				),
+				'credential' => array(
+					'name'          => '',
+					'schema'        => 'Bearer',
+					'oauth_url'     => 'https://accounts.google.com/o/oauth2/v2',
+					'scope'         => 'https://www.googleapis.com/auth/calendar.readonly https://www.googleapis.com/auth/calendar.events',
+					'client_id'     => '',
+					'client_secret' => '',
+					'access_token'  => '',
+					'expires_at'    => 0,
+					'refresh_token' => '',
+				),
+			),
+			$defaults,
+			$schema
+		);
+
+		return $defaults;
+	},
+	10,
+	3
+);
+
+add_filter(
+	'forms_bridge_template_data',
+	function ( $data, $template_id ) {
+		if ( strpos( $template_id, 'gcalendar-' ) !== 0 ) {
+			return $data;
+		}
+
+		$data['bridge']['endpoint'] = '/calendar/v3/calendars/' . $data['bridge']['endpoint'] . '/events';
+		return $data;
+	},
+	10,
+	2
+);
+
+add_filter(
+	'http_bridge_oauth_url',
+	function ( $url, $verb ) {
+		if ( false === strpos( $url, 'accounts.google.com' ) ) {
+			return $url;
+		}
+
+		if ( 'auth' === $verb ) {
+			return $url;
+		}
+
+		return "https://oauth2.googleapis.com/{$verb}";
+	},
+	10,
+	2
+);
diff --git a/forms-bridge/addons/gcalendar/jobs/event-dates.php b/forms-bridge/addons/gcalendar/jobs/event-dates.php
new file mode 100644
index 00000000..250dcb1b
--- /dev/null
+++ b/forms-bridge/addons/gcalendar/jobs/event-dates.php
@@ -0,0 +1,88 @@
+<?php
+/**
+ * Google Calendar event dates job
+ *
+ * @package formsbridge
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit();
+}
+
+return array(
+	'title'       => __( 'Event dates', 'forms-bridge' ),
+	'description' => array(
+		'Given a datetime and a duration in hours and minuts, sets up the event dates',
+		'forms-bridge',
+	),
+	'method'      => 'forms_bridge_gcalendar_event_dates',
+	'input'       => array(
+		array(
+			'name'     => 'datetime',
+			'schema'   => array( 'type' => 'string' ),
+			'required' => true,
+		),
+		array(
+			'name'     => 'duration_hours',
+			'schema'   => array( 'type' => 'string' ),
+			'required' => true,
+		),
+		array(
+			'name'   => 'duration_minutes',
+			'schema' => array( 'type' => 'string' ),
+		),
+	),
+	'output'      => array(
+		array(
+			'name'   => 'start',
+			'schema' => array(
+				'type'                 => 'object',
+				'properties'           => array(
+					'dateTime' => array( 'type' => 'string' ),
+					'timeZone' => array( 'type' => 'string' ),
+				),
+				'additionalProperties' => false,
+				'required'             => array( 'dateTime' ),
+			),
+		),
+		array(
+			'name'   => 'end',
+			'schema' => array(
+				'type'                 => 'object',
+				'properties'           => array(
+					'dateTime' => array( 'type' => 'string' ),
+					'timeZone' => array( 'type' => 'string' ),
+				),
+				'additionalProperties' => false,
+				'required'             => array( 'dateTime' ),
+			),
+		),
+	),
+);
+
+/**
+ * Given a datetime and a duration in hours and minuts, sets up the event dates,
+ *
+ * @param array $payload Bridge payload.
+ *
+ * @return array
+ */
+function forms_bridge_gcalendar_event_dates( $payload ) {
+	$datetime = $payload['datetime'];
+	$time     = strtotime( $datetime );
+	$endtime  = $time + $payload['duration_hours'] * 3600 + ( $payload['duration_minutes'] ?? 0 ) * 60;
+
+	$timezone = wp_timezone_string();
+
+	$payload['start'] = array(
+		'dateTime' => gmdate( 'Y-m-d\TH:i:s', $time ),
+		'timeZone' => $timezone,
+	);
+
+	$payload['end'] = array(
+		'dateTime' => gmdate( 'Y-m-d\TH:i:s', $endtime ),
+		'timeZone' => $timezone,
+	);
+
+	return $payload;
+}
diff --git a/forms-bridge/addons/gcalendar/templates/meetings.php b/forms-bridge/addons/gcalendar/templates/meetings.php
new file mode 100644
index 00000000..719a0ace
--- /dev/null
+++ b/forms-bridge/addons/gcalendar/templates/meetings.php
@@ -0,0 +1,221 @@
+<?php
+/**
+ * Google Calendar meetings bridge template
+ *
+ * @package formsbridge
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit();
+}
+
+return array(
+	'title'       => __( 'Meetings', 'forms-bridge' ),
+	'description' => __(
+		'Meetings bridge template. The resulting bridge will convert form submission into Google Calendar events.',
+		'forms-bridge',
+	),
+	'bridge'      => array(
+		'workflow'  => array( 'date-fields-to-date', 'event-dates' ),
+		'mutations' => array(
+			array(
+				array(
+					'from' => 'email',
+					'to'   => 'attendees[0].email',
+					'cast' => 'string',
+				),
+				array(
+					'from' => 'summary',
+					'to'   => 'attendees[0].displayName',
+					'cast' => 'copy',
+				),
+			),
+		),
+	),
+	'form'        => array(
+		'title'  => __( 'Meetings', 'forms-bridge' ),
+		'fields' => array(
+			array(
+				'name'  => 'summary',
+				'label' => __( 'Your Name', 'forms-bridge' ),
+				'type'  => 'text',
+			),
+			array(
+				'name'  => 'email',
+				'label' => __( 'Your Email', 'forms-bridge' ),
+				'type'  => 'email',
+			),
+			array(
+				'name'  => 'description',
+				'label' => __( 'Comments', 'forms-bridge' ),
+				'type'  => 'textarea',
+			),
+			array(
+				'name'     => 'date',
+				'label'    => __( 'Date', 'forms-bridge' ),
+				'type'     => 'date',
+				'required' => true,
+			),
+			array(
+				'name'     => 'hour',
+				'label'    => __( 'Hour', 'forms-bridge' ),
+				'type'     => 'select',
+				'required' => true,
+				'options'  => array(
+					array(
+						'label' => __( '1 AM', 'forms-bridge' ),
+						'value' => '01',
+					),
+					array(
+						'label' => __( '2 AM', 'forms-bridge' ),
+						'value' => '02',
+					),
+					array(
+						'label' => __( '3 AM', 'forms-bridge' ),
+						'value' => '03',
+					),
+					array(
+						'label' => __( '4 AM', 'forms-bridge' ),
+						'value' => '04',
+					),
+					array(
+						'label' => __( '5 AM', 'forms-bridge' ),
+						'value' => '05',
+					),
+					array(
+						'label' => __( '6 AM', 'forms-bridge' ),
+						'value' => '06',
+					),
+					array(
+						'label' => __( '7 AM', 'forms-bridge' ),
+						'value' => '07',
+					),
+					array(
+						'label' => __( '8 AM', 'forms-bridge' ),
+						'value' => '08',
+					),
+					array(
+						'label' => __( '9 AM', 'forms-bridge' ),
+						'value' => '09',
+					),
+					array(
+						'label' => __( '10 AM', 'forms-bridge' ),
+						'value' => '10',
+					),
+					array(
+						'label' => __( '11 AM', 'forms-bridge' ),
+						'value' => '11',
+					),
+					array(
+						'label' => __( '12 AM', 'forms-bridge' ),
+						'value' => '12',
+					),
+					array(
+						'label' => __( '1 PM', 'forms-bridge' ),
+						'value' => '13',
+					),
+					array(
+						'label' => __( '2 PM', 'forms-bridge' ),
+						'value' => '14',
+					),
+					array(
+						'label' => __( '3 PM', 'forms-bridge' ),
+						'value' => '15',
+					),
+					array(
+						'label' => __( '4 PM', 'forms-bridge' ),
+						'value' => '16',
+					),
+					array(
+						'label' => __( '5 PM', 'forms-bridge' ),
+						'value' => '17',
+					),
+					array(
+						'label' => __( '6 PM', 'forms-bridge' ),
+						'value' => '18',
+					),
+					array(
+						'label' => __( '7 PM', 'forms-bridge' ),
+						'value' => '19',
+					),
+					array(
+						'label' => __( '8 PM', 'forms-bridge' ),
+						'value' => '20',
+					),
+					array(
+						'label' => __( '9 PM', 'forms-bridge' ),
+						'value' => '21',
+					),
+					array(
+						'label' => __( '10 PM', 'forms-bridge' ),
+						'value' => '22',
+					),
+					array(
+						'label' => __( '11 PM', 'forms-bridge' ),
+						'value' => '23',
+					),
+					array(
+						'label' => __( '12 PM', 'forms-bridge' ),
+						'value' => '24',
+					),
+				),
+			),
+			array(
+				'name'     => 'minute',
+				'label'    => __( 'Minute', 'forms-bridge' ),
+				'type'     => 'select',
+				'required' => true,
+				'options'  => array(
+					array(
+						'label' => '00',
+						'value' => '00.0',
+					),
+					array(
+						'label' => '05',
+						'value' => '05',
+					),
+					array(
+						'label' => '10',
+						'value' => '10',
+					),
+					array(
+						'label' => '15',
+						'value' => '15',
+					),
+					array(
+						'label' => '20',
+						'value' => '20',
+					),
+					array(
+						'label' => '25',
+						'value' => '25',
+					),
+					array(
+						'label' => '30',
+						'value' => '30',
+					),
+					array(
+						'label' => '35',
+						'value' => '35',
+					),
+					array(
+						'label' => '40',
+						'value' => '40',
+					),
+					array(
+						'label' => '45',
+						'value' => '45',
+					),
+					array(
+						'label' => '50',
+						'value' => '50',
+					),
+					array(
+						'label' => '55',
+						'value' => '55',
+					),
+				),
+			),
+		),
+	),
+);
diff --git a/forms-bridge/addons/gsheets/class-gsheets-form-bridge.php b/forms-bridge/addons/gsheets/class-gsheets-form-bridge.php
index cd93cfb6..8d855fde 100644
--- a/forms-bridge/addons/gsheets/class-gsheets-form-bridge.php
+++ b/forms-bridge/addons/gsheets/class-gsheets-form-bridge.php
@@ -186,6 +186,9 @@ public function submit( $payload = array(), $attachments = array() ) {
 		}
 
 		$backend = $this->backend;
+		if ( ! $backend ) {
+			return new WP_Error( 'invalid_backend', 'Backend not found' );
+		}
 
 		$sheets = $this->get_sheets( $backend );
 		if ( is_wp_error( $sheets ) ) {
diff --git a/forms-bridge/addons/suitecrm/hooks.php b/forms-bridge/addons/suitecrm/hooks.php
index b53729c3..75dbc4d1 100644
--- a/forms-bridge/addons/suitecrm/hooks.php
+++ b/forms-bridge/addons/suitecrm/hooks.php
@@ -101,7 +101,7 @@ function ( $defaults, $addon, $schema ) {
 						'name'        => 'base_url',
 						'label'       => __( 'SuiteCRM URL', 'forms-bridge' ),
 						'description' => __(
-							'Base URL of your SuiteCRM installation (e.g., https://crm.example.com)',
+							'Base URL of your SuiteCRM installation (e.g., https://crm.example.coop)',
 							'forms-bridge'
 						),
 						'type'        => 'url',
diff --git a/forms-bridge/addons/vtiger/hooks.php b/forms-bridge/addons/vtiger/hooks.php
index a11aee77..ab4e9f21 100644
--- a/forms-bridge/addons/vtiger/hooks.php
+++ b/forms-bridge/addons/vtiger/hooks.php
@@ -104,7 +104,7 @@ function ( $defaults, $addon, $schema ) {
 						'name'        => 'base_url',
 						'label'       => __( 'Vtiger URL', 'forms-bridge' ),
 						'description' => __(
-							'Base URL of your Vtiger installation (e.g., https://crm.example.com)',
+							'Base URL of your Vtiger installation (e.g., https://crm.example.coop)',
 							'forms-bridge'
 						),
 						'type'        => 'url',
diff --git a/forms-bridge/readme.txt b/forms-bridge/readme.txt
index 03bd41c7..d069c32b 100644
--- a/forms-bridge/readme.txt
+++ b/forms-bridge/readme.txt
@@ -36,6 +36,7 @@ Forms Bridge has the following addons:
 * [Brevo](https://formsbridge.codeccoop.org/documentation/brevo/)

 * [Dolibarr](https://formsbridge.codeccoop.org/documentation/dolibarr/)

 * [FinanCoop](https://formsbridge.codeccoop.org/documentation/financoop/)

+* [Google Calendar](https://formsbridge.codeccoop.org/documentation/google-calendar/)

 * [Google Sheets](https://formsbridge.codeccoop.org/documentation/google-sheets/)

 * [Holded](https://formsbridge.codeccoop.org/documentation/holded/)

 * [Listmonk](https://formsbridge.codeccoop.org/documentation/listmonk/)

diff --git a/tests/addons/test-gcalendar.php b/tests/addons/test-gcalendar.php
new file mode 100644
index 00000000..ef7dcd3e
--- /dev/null
+++ b/tests/addons/test-gcalendar.php
@@ -0,0 +1,708 @@
+<?php
+/**
+ * Class GCalendarTest
+ *
+ * @package formsbridge-tests
+ */
+
+use FORMS_BRIDGE\GCalendar_Form_Bridge;
+use FORMS_BRIDGE\GCalendar_Addon;
+use FORMS_BRIDGE\Addon;
+use HTTP_BRIDGE\Backend;
+use HTTP_BRIDGE\Credential;
+
+/**
+ * Google Calendar addon test case.
+ */
+class GCalendarTest 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;
+
+	/**
+	 * Test credential provider.
+	 *
+	 * @return Credential[]
+	 */
+	public static function credentials_provider() {
+		return array(
+			new Credential(
+				array(
+					'name'          => 'gcalendar-test-credential',
+					'schema'        => 'Bearer',
+					'oauth_url'     => 'https://accounts.google.com/o/oauth2/v2',
+					'client_id'     => 'test-client-id',
+					'client_secret' => 'test-client-secret',
+					'access_token'  => 'test-access-token-12345',
+					'expires_at'    => time() + 3600,
+					'refresh_token' => 'test-refresh-token',
+				)
+			),
+		);
+	}
+
+	/**
+	 * Test backend provider.
+	 *
+	 * @return Backend[]
+	 */
+	public static function backends_provider() {
+		return array(
+			new Backend(
+				array(
+					'name'       => 'gcalendar-test-backend',
+					'base_url'   => 'https://www.googleapis.com',
+					'credential' => 'gcalendar-test-credential',
+					'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,
+		);
+
+		// Parse the URL to determine the operation.
+		$parsed_url = wp_parse_url( $url );
+		$path       = $parsed_url['path'] ?? '';
+
+		// Return appropriate mock response based on path and method.
+		if ( self::$mock_response ) {
+			$response_body = self::$mock_response;
+		} else {
+			$response_body = self::get_mock_response( $path, $args );
+		}
+
+		return array(
+			'response'      => array(
+				'code'    => 200,
+				'message' => 'Success',
+			),
+			'headers'       => array( 'Content-Type' => 'application/json' ),
+			'cookies'       => array(),
+			'body'          => wp_json_encode( $response_body ),
+			'http_response' => null,
+		);
+	}
+
+	/**
+	 * Get mock response based on API path.
+	 *
+	 * @param string $path API path.
+	 * @param array  $args Request arguments.
+	 *
+	 * @return array Mock response.
+	 */
+	private static function get_mock_response( $path, $args ) {
+		$method = $args['method'] ?? 'GET';
+
+		if ( strpos( $path, '/calendarList' ) !== false ) {
+			// Calendar list endpoint.
+			return array(
+				'kind'  => 'calendar#calendarList',
+				'items' => array(
+					array(
+						'id'      => 'primary',
+						'summary' => 'Primary Calendar',
+					),
+					array(
+						'id'      => 'test@group.calendar.google.com',
+						'summary' => 'Test Calendar',
+					),
+				),
+			);
+		}
+
+		if ( strpos( $path, '/events' ) !== false && 'POST' === $method ) {
+			// Create event endpoint.
+			$body  = json_decode( $args['body'], true );
+			$event = array_merge(
+				array(
+					'kind'     => 'calendar#event',
+					'id'       => 'test-event-id-' . time(),
+					'status'   => 'confirmed',
+					'htmlLink' => 'https://www.google.com/calendar/event?eid=test',
+					'created'  => gmdate( 'c' ),
+					'updated'  => gmdate( 'c' ),
+				),
+				$body
+			);
+			return $event;
+		}
+
+		if ( strpos( $path, '/events' ) !== false && 'PUT' === $method ) {
+			// Update event endpoint.
+			$body = json_decode( $args['body'], true );
+			return array_merge(
+				array(
+					'kind'    => 'calendar#event',
+					'id'      => 'test-event-id-12345',
+					'status'  => 'confirmed',
+					'updated' => gmdate( 'c' ),
+				),
+				$body
+			);
+		}
+
+		// Default response.
+		return array(
+			'success' => true,
+		);
+	}
+
+	/**
+	 * Set up test fixtures.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		self::$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\GCalendar_Addon' ) );
+		$this->assertEquals( 'Google Calendar', GCalendar_Addon::TITLE );
+		$this->assertEquals( 'gcalendar', GCalendar_Addon::NAME );
+		$this->assertEquals( '\FORMS_BRIDGE\GCalendar_Form_Bridge', GCalendar_Addon::BRIDGE );
+	}
+
+	/**
+	 * Test that the form bridge class exists.
+	 */
+	public function test_form_bridge_class_exists() {
+		$this->assertTrue( class_exists( 'FORMS_BRIDGE\GCalendar_Form_Bridge' ) );
+	}
+
+	/**
+	 * Test bridge validation with valid data.
+	 */
+	public function test_bridge_validation() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-gcalendar-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$this->assertTrue( $bridge->is_valid );
+	}
+
+	/**
+	 * Test bridge validation with invalid data.
+	 */
+	public function test_bridge_validation_invalid() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name' => 'invalid-bridge',
+				// Missing required fields.
+			)
+		);
+
+		$this->assertTrue( $bridge->is_valid );
+	}
+
+	/**
+	 * Test creating a calendar event with all fields.
+	 */
+	public function test_create_event() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-create-event-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary'     => 'Team Meeting',
+			'description' => 'Weekly team sync meeting',
+			'location'    => 'Conference Room A',
+			'start'       => '2024-03-20T10:00:00',
+			'end'         => '2024-03-20T11:00:00',
+			'attendees'   => 'john@example.coop,jane@example.coop',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertArrayHasKey( 'id', $response['data'] );
+		$this->assertEquals( 'Team Meeting', $response['data']['summary'] );
+		$this->assertEquals( 'Weekly team sync meeting', $response['data']['description'] );
+		$this->assertEquals( 'Conference Room A', $response['data']['location'] );
+	}
+
+	/**
+	 * Test creating event with minimal fields.
+	 */
+	public function test_create_event_minimal() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-minimal-event-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary' => 'Quick Meeting',
+			'start'   => '2024-03-20T14:00:00',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertEquals( 'Quick Meeting', $response['data']['summary'] );
+		$this->assertArrayHasKey( 'end', $response['data'] );
+	}
+
+	/**
+	 * Test creating event with numeric timestamp.
+	 */
+	public function test_create_event_with_timestamp() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-timestamp-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$start_time = strtotime( '2024-03-20 10:00:00' );
+		$end_time   = strtotime( '2024-03-20 11:00:00' );
+
+		$payload = array(
+			'summary' => 'Timestamp Event',
+			'start'   => $start_time,
+			'end'     => $end_time,
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertArrayHasKey( 'start', $response['data'] );
+		$this->assertArrayHasKey( 'dateTime', $response['data']['start'] );
+	}
+
+	/**
+	 * Test creating event with attendees as array.
+	 */
+	public function test_create_event_attendees_array() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-attendees-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary'   => 'Team Meeting',
+			'start'     => '2024-03-20T10:00:00',
+			'attendees' => array( 'john@example.coop', 'jane@example.coop' ),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertArrayHasKey( 'attendees', $response['data'] );
+		$this->assertCount( 2, $response['data']['attendees'] );
+	}
+
+	/**
+	 * Test creating event with structured attendees.
+	 */
+	public function test_create_event_attendees_structured() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-structured-attendees-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary'   => 'Important Meeting',
+			'start'     => '2024-03-20T10:00:00',
+			'attendees' => array(
+				array(
+					'email'    => 'john@example.coop',
+					'optional' => false,
+				),
+				array(
+					'email'    => 'jane@example.coop',
+					'optional' => true,
+				),
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'attendees', $response['data'] );
+	}
+
+	/**
+	 * Test error when summary is missing.
+	 */
+	public function test_error_missing_summary() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-missing-summary-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'start' => '2024-03-20T10:00:00',
+			'end'   => '2024-03-20T11:00:00',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertTrue( is_wp_error( $response ) );
+		$this->assertEquals( 'missing_summary', $response->get_error_code() );
+	}
+
+	/**
+	 * Test error when start date is missing.
+	 */
+	public function test_error_missing_start_date() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-missing-start-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary' => 'Meeting',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertTrue( is_wp_error( $response ) );
+		$this->assertEquals( 'missing_event_dates', $response->get_error_code() );
+	}
+
+	/**
+	 * Test automatic end time calculation.
+	 */
+	public function test_auto_end_time() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-auto-end-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary' => 'Auto End Meeting',
+			'start'   => '2024-03-20T10:00:00',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'end', $response['data'] );
+		$this->assertArrayHasKey( 'dateTime', $response['data']['end'] );
+	}
+
+	/**
+	 * Test creating event with color.
+	 */
+	public function test_create_event_with_color() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-color-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary' => 'Colored Event',
+			'start'   => '2024-03-20T10:00:00',
+			'colorId' => '5',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'colorId', $response['data'] );
+		$this->assertEquals( '5', $response['data']['colorId'] );
+	}
+
+	/**
+	 * Test creating event with reminders.
+	 */
+	public function test_create_event_with_reminders() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-reminders-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary'   => 'Event with Reminders',
+			'start'     => '2024-03-20T10:00:00',
+			'reminders' => array(
+				'useDefault' => false,
+				'overrides'  => array(
+					array(
+						'method'  => 'email',
+						'minutes' => 1440,
+					),
+					array(
+						'method'  => 'popup',
+						'minutes' => 10,
+					),
+				),
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'reminders', $response['data'] );
+	}
+
+	/**
+	 * Test invalid backend handling.
+	 */
+	public function test_invalid_backend() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-invalid-backend-bridge',
+				'backend'  => 'non-existent-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary' => 'Test Event',
+			'start'   => '2024-03-20T10:00:00',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertTrue( is_wp_error( $response ) );
+		$this->assertEquals( 'invalid_backend', $response->get_error_code() );
+	}
+
+	/**
+	 * Test addon ping method.
+	 */
+	public function test_addon_ping() {
+		$addon    = Addon::addon( 'gcalendar' );
+		$response = $addon->ping( 'gcalendar-test-backend' );
+
+		$this->assertTrue( $response );
+	}
+
+	/**
+	 * Test addon ping with invalid backend.
+	 */
+	public function test_addon_ping_invalid_backend() {
+		Backend::temp_registration(
+			array(
+				'name'       => 'gcalendar-invalid-host-backend',
+				'base_url'   => 'https://wrong.example.coop',
+				'credential' => 'gcalendar-test-credential',
+				'headers'    => array(),
+			)
+		);
+
+		$addon    = Addon::addon( 'gcalendar' );
+		$response = $addon->ping( 'gcalendar-invalid-host-backend' );
+
+		$this->assertFalse( $response );
+	}
+
+	/**
+	 * Test addon get_endpoint_schema method for POST.
+	 */
+	public function test_addon_get_endpoint_schema_post() {
+		Backend::temp_registration(
+			array(
+				'name'       => 'gcalendar-test-backend',
+				'base_url'   => 'https://www.googleapis.com',
+				'credential' => 'gcalendar-test-credential',
+				'headers'    => array(),
+			)
+		);
+
+		$addon  = Addon::addon( 'gcalendar' );
+		$schema = $addon->get_endpoint_schema(
+			'/calendar/v3/calendars/primary/events',
+			'gcalendar-test-backend',
+			'POST'
+		);
+
+		$this->assertIsArray( $schema );
+		$this->assertNotEmpty( $schema );
+
+		$field_names = array_column( $schema, 'name' );
+		$this->assertContains( 'summary', $field_names );
+		$this->assertContains( 'description', $field_names );
+		$this->assertContains( 'location', $field_names );
+		$this->assertContains( 'start', $field_names );
+		$this->assertContains( 'end', $field_names );
+		$this->assertContains( 'attendees', $field_names );
+	}
+
+	/**
+	 * Test addon get_endpoint_schema method for GET returns empty.
+	 */
+	public function test_addon_get_endpoint_schema_get() {
+		Backend::temp_registration(
+			array(
+				'name'       => 'gcalendar-test-backend',
+				'base_url'   => 'https://www.googleapis.com',
+				'credential' => 'gcalendar-test-credential',
+				'headers'    => array(),
+			)
+		);
+
+		$addon  = Addon::addon( 'gcalendar' );
+		$schema = $addon->get_endpoint_schema(
+			'/calendar/v3/calendars/primary/events',
+			'gcalendar-test-backend',
+			'GET'
+		);
+
+		$this->assertIsArray( $schema );
+		$this->assertEmpty( $schema );
+	}
+
+	/**
+	 * Test invalid email in attendees is filtered out.
+	 */
+	public function test_invalid_email_filtered() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-invalid-email-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary'   => 'Meeting',
+			'start'     => '2024-03-20T10:00:00',
+			'attendees' => 'valid@example.coop,invalid-email,another@example.coop',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'attendees', $response['data'] );
+		$this->assertCount( 2, $response['data']['attendees'] );
+	}
+
+	/**
+	 * Test creating event with already structured datetime.
+	 */
+	public function test_structured_datetime() {
+		$bridge = new GCalendar_Form_Bridge(
+			array(
+				'name'     => 'test-structured-datetime-bridge',
+				'backend'  => 'gcalendar-test-backend',
+				'endpoint' => '/calendar/v3/calendars/primary/events',
+				'method'   => 'POST',
+			)
+		);
+
+		$payload = array(
+			'summary' => 'Structured DateTime Event',
+			'start'   => array(
+				'dateTime' => '2024-03-20T10:00:00',
+				'timeZone' => 'America/New_York',
+			),
+			'end'     => array(
+				'dateTime' => '2024-03-20T11:00:00',
+				'timeZone' => 'America/New_York',
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'start', $response['data'] );
+		$this->assertEquals( '2024-03-20T10:00:00', $response['data']['start']['dateTime'] );
+		$this->assertEquals( 'America/New_York', $response['data']['start']['timeZone'] );
+	}
+}
diff --git a/tests/addons/test-gsheets.php b/tests/addons/test-gsheets.php
index 7574d3ba..40a19a69 100644
--- a/tests/addons/test-gsheets.php
+++ b/tests/addons/test-gsheets.php
@@ -1,14 +1,834 @@
 <?php
 /**
- * Class GoogleSheetsTest
+ * Class GSheetsTest
  *
  * @package formsbridge-tests
  */
 
 use FORMS_BRIDGE\GSheets_Form_Bridge;
+use FORMS_BRIDGE\GSheets_Addon;
+use FORMS_BRIDGE\Addon;
+use HTTP_BRIDGE\Backend;
+use HTTP_BRIDGE\Credential;
 
 /**
- * Google Sheets test case.
+ * Google Sheets addon test case.
  */
 class GSheetsTest 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;
+
+	/**
+	 * Mock spreadsheet ID.
+	 *
+	 * @var string
+	 */
+	private const SPREADSHEET_ID = '1BxiMVs0XRA5nFMdKvBdBZjgmUUqptlbs74OgvE2upms';
+
+	/**
+	 * Test credential provider.
+	 *
+	 * @return Credential[]
+	 */
+	public static function credentials_provider() {
+		return array(
+			new Credential(
+				array(
+					'name'          => 'gsheets-test-credential',
+					'schema'        => 'Bearer',
+					'oauth_url'     => 'https://accounts.google.com/o/oauth2/v2',
+					'client_id'     => 'test-client-id',
+					'client_secret' => 'test-client-secret',
+					'access_token'  => 'test-access-token-12345',
+					'expires_at'    => time() + 3600,
+					'refresh_token' => 'test-refresh-token',
+				)
+			),
+		);
+	}
+
+	/**
+	 * Test backend provider.
+	 *
+	 * @return Backend[]
+	 */
+	public static function backends_provider() {
+		return array(
+			new Backend(
+				array(
+					'name'       => 'gsheets-test-backend',
+					'base_url'   => 'https://sheets.googleapis.com/v4/spreadsheets',
+					'credential' => 'gsheets-test-credential',
+					'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,
+		);
+
+		// Parse the URL to determine the operation.
+		$parsed_url = wp_parse_url( $url );
+		$path       = $parsed_url['path'] ?? '';
+		$query      = $parsed_url['query'] ?? '';
+
+		// Return appropriate mock response based on path and method.
+		if ( self::$mock_response ) {
+			$response_body = self::$mock_response;
+		} else {
+			$response_body = self::get_mock_response( $path, $query, $args );
+		}
+
+		return array(
+			'response'      => array(
+				'code'    => 200,
+				'message' => 'Success',
+			),
+			'headers'       => array( 'Content-Type' => 'application/json' ),
+			'cookies'       => array(),
+			'body'          => wp_json_encode( $response_body ),
+			'http_response' => null,
+		);
+	}
+
+	/**
+	 * Get mock response based on API path.
+	 *
+	 * @param string $path API path.
+	 * @param string $query Query string.
+	 * @param array  $args Request arguments.
+	 *
+	 * @return array Mock response.
+	 */
+	private static function get_mock_response( $path, $query, $args ) {
+		$method = $args['method'] ?? 'GET';
+
+		// Get spreadsheet metadata (list of sheets).
+		if ( preg_match( '/\/spreadsheets\/([^\/]+)$/', $path, $matches ) && 'GET' === $method ) {
+			return array(
+				'spreadsheetId' => self::SPREADSHEET_ID,
+				'properties'    => array(
+					'title'    => 'Test Spreadsheet',
+					'locale'   => 'en_US',
+					'timeZone' => 'America/New_York',
+				),
+				'sheets'        => array(
+					array(
+						'properties' => array(
+							'sheetId'   => 0,
+							'title'     => 'Sheet1',
+							'index'     => 0,
+							'sheetType' => 'GRID',
+						),
+					),
+					array(
+						'properties' => array(
+							'sheetId'   => 1234567890,
+							'title'     => 'Contacts',
+							'index'     => 1,
+							'sheetType' => 'GRID',
+						),
+					),
+				),
+			);
+		}
+
+		// Get sheet values (headers or data).
+		if ( strpos( $path, '/values/' ) !== false && 'GET' === $method ) {
+			// Extract sheet name from path.
+			if ( preg_match( '/\/values\/([^!]+)!/', $path, $matches ) ) {
+				$sheet = urldecode( $matches[1] );
+
+				// Return headers for the first row request.
+				if ( strpos( $path, '!1:1' ) !== false ) {
+					return array(
+						'range'          => "{$sheet}!A1:Z1",
+						'majorDimension' => 'ROWS',
+						'values'         => array(
+							array( 'Name', 'Email', 'Phone', 'Company' ),
+						),
+					);
+				}
+
+				// Return data rows.
+				return array(
+					'range'          => "{$sheet}!A1:D10",
+					'majorDimension' => 'ROWS',
+					'values'         => array(
+						array( 'Name', 'Email', 'Phone', 'Company' ),
+						array( 'John Doe', 'john@example.coop', '555-1234', 'Acme Corp' ),
+						array( 'Jane Smith', 'jane@example.coop', '555-5678', 'Test Inc' ),
+					),
+				);
+			}
+
+			return array(
+				'range'          => 'Sheet1!A1:Z1',
+				'majorDimension' => 'ROWS',
+				'values'         => array(),
+			);
+		}
+
+		// Append values to sheet.
+		if ( strpos( $path, '/values/' ) !== false && strpos( $path, ':append' ) !== false && 'POST' === $method ) {
+			$body = json_decode( $args['body'], true );
+			return array(
+				'spreadsheetId' => self::SPREADSHEET_ID,
+				'tableRange'    => 'Contacts!A1:D1',
+				'updates'       => array(
+					'spreadsheetId'  => self::SPREADSHEET_ID,
+					'updatedRange'   => 'Contacts!A2:D2',
+					'updatedRows'    => 1,
+					'updatedColumns' => 4,
+					'updatedCells'   => 4,
+				),
+			);
+		}
+
+		// Create new sheet (batchUpdate).
+		if ( strpos( $path, ':batchUpdate' ) !== false && 'POST' === $method ) {
+			$body = json_decode( $args['body'], true );
+			return array(
+				'spreadsheetId' => self::SPREADSHEET_ID,
+				'replies'       => array(
+					array(
+						'addSheet' => array(
+							'properties' => array(
+								'sheetId'   => time(),
+								'title'     => $body['requests'][0]['addSheet']['properties']['title'] ?? 'New Sheet',
+								'index'     => $body['requests'][0]['addSheet']['properties']['index'] ?? 0,
+								'sheetType' => 'GRID',
+							),
+						),
+					),
+				),
+			);
+		}
+
+		// List spreadsheets (Drive API).
+		if ( strpos( $path, '/drive/v3/files' ) !== false ) {
+			return array(
+				'kind'  => 'drive#fileList',
+				'files' => array(
+					array(
+						'id'       => self::SPREADSHEET_ID,
+						'name'     => 'Test Spreadsheet',
+						'mimeType' => 'application/vnd.google-apps.spreadsheet',
+					),
+					array(
+						'id'       => '2CxjNWt1YSB6oGNeLvCeEZkmVVrqsumct85PhuF3vqnt',
+						'name'     => 'Another Spreadsheet',
+						'mimeType' => 'application/vnd.google-apps.spreadsheet',
+					),
+				),
+			);
+		}
+
+		// Default response.
+		return array(
+			'success' => true,
+		);
+	}
+
+	/**
+	 * Set up test fixtures.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		self::$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\GSheets_Addon' ) );
+		$this->assertEquals( 'Google Sheets', GSheets_Addon::TITLE );
+		$this->assertEquals( 'gsheets', GSheets_Addon::NAME );
+		$this->assertEquals( '\FORMS_BRIDGE\GSheets_Form_Bridge', GSheets_Addon::BRIDGE );
+	}
+
+	/**
+	 * Test that the form bridge class exists.
+	 */
+	public function test_form_bridge_class_exists() {
+		$this->assertTrue( class_exists( 'FORMS_BRIDGE\GSheets_Form_Bridge' ) );
+	}
+
+	/**
+	 * Test bridge validation with valid data.
+	 */
+	public function test_bridge_validation() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-gsheets-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$this->assertTrue( $bridge->is_valid );
+	}
+
+	/**
+	 * Test bridge validation with invalid data.
+	 */
+	public function test_bridge_validation_invalid() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name' => 'invalid-bridge',
+				// Missing required fields.
+			)
+		);
+
+		$this->assertTrue( $bridge->is_valid );
+	}
+
+	/**
+	 * Test appending data to existing sheet.
+	 */
+	public function test_append_to_existing_sheet() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-append-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$payload = array(
+			'Name'    => 'Alice Johnson',
+			'Email'   => 'alice@example.coop',
+			'Phone'   => '555-9999',
+			'Company' => 'NewCo',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertArrayHasKey( 'updates', $response['data'] );
+		$this->assertEquals( 1, $response['data']['updates']['updatedRows'] );
+	}
+
+	/**
+	 * Test appending data to new sheet (auto-creates sheet).
+	 */
+	public function test_append_to_new_sheet() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-new-sheet-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'NewSheet',
+			)
+		);
+
+		$payload = array(
+			'Name'  => 'Bob Smith',
+			'Email' => 'bob@example.coop',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
+
+	/**
+	 * Test appending data with headers auto-creation.
+	 */
+	public function test_append_creates_headers() {
+		// Mock empty headers response.
+		self::$mock_response = array(
+			'range'          => 'EmptySheet!A1:Z1',
+			'majorDimension' => 'ROWS',
+			'values'         => array(),
+		);
+
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-headers-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'EmptySheet',
+			)
+		);
+
+		// Reset mock after getting sheets list.
+		add_filter(
+			'pre_http_request',
+			function ( $pre, $args, $url ) {
+				if ( strpos( $url, '/values/' ) !== false && strpos( $url, '!1:1' ) !== false ) {
+					return array(
+						'response'      => array(
+							'code'    => 200,
+							'message' => 'Success',
+						),
+						'headers'       => array( 'Content-Type' => 'application/json' ),
+						'cookies'       => array(),
+						'body'          => wp_json_encode(
+							array(
+								'range'          => 'EmptySheet!A1:Z1',
+								'majorDimension' => 'ROWS',
+								'values'         => array(),
+							)
+						),
+						'http_response' => null,
+					);
+				}
+				return $pre;
+			},
+			11,
+			3
+		);
+
+		$payload = array(
+			'Field1' => 'Value1',
+			'Field2' => 'Value2',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+	}
+
+	/**
+	 * Test flattening nested payload.
+	 */
+	public function test_flatten_nested_payload() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-flatten-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$payload = array(
+			'Name'    => 'Test User',
+			'Email'   => 'test@example.coop',
+			'Address' => array(
+				'Street' => '123 Main St',
+				'City'   => 'New York',
+				'State'  => 'NY',
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
+
+	/**
+	 * Test flattening array values to comma-separated string.
+	 */
+	public function test_flatten_array_values() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-array-values-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$payload = array(
+			'Name'     => 'Test User',
+			'Email'    => 'test@example.coop',
+			'Tags'     => array( 'customer', 'premium', 'active' ),
+			'Products' => array( 'Product A', 'Product B' ),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
+
+	/**
+	 * Test getting headers from sheet.
+	 */
+	public function test_get_headers() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-headers-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$headers = $bridge->get_headers();
+
+		$this->assertFalse( is_wp_error( $headers ) );
+		$this->assertIsArray( $headers );
+		$this->assertContains( 'Name', $headers );
+		$this->assertContains( 'Email', $headers );
+		$this->assertContains( 'Phone', $headers );
+		$this->assertContains( 'Company', $headers );
+	}
+
+	/**
+	 * Test error when backend is invalid.
+	 */
+	public function test_error_invalid_backend() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-invalid-backend-bridge',
+				'backend'  => 'non-existent-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$response = $bridge->submit( array( 'Name' => 'Test' ) );
+
+		$this->assertTrue( is_wp_error( $response ) );
+		$this->assertEquals( 'invalid_backend', $response->get_error_code() );
+	}
+
+	/**
+	 * Test addon ping method.
+	 */
+	public function test_addon_ping() {
+		$addon    = Addon::addon( 'gsheets' );
+		$response = $addon->ping( 'gsheets-test-backend' );
+
+		$this->assertTrue( $response );
+	}
+
+	/**
+	 * Test addon ping with invalid backend host.
+	 */
+	public function test_addon_ping_invalid_host() {
+		Backend::temp_registration(
+			array(
+				'name'       => 'gsheets-invalid-host-backend',
+				'base_url'   => 'https://wrong.example.coop',
+				'credential' => 'gsheets-test-credential',
+				'headers'    => array(),
+			)
+		);
+
+		$addon    = Addon::addon( 'gsheets' );
+		$response = $addon->ping( 'gsheets-invalid-host-backend' );
+
+		$this->assertFalse( $response );
+	}
+
+	/**
+	 * Test addon ping without credential.
+	 */
+	public function test_addon_ping_no_credential() {
+		Backend::temp_registration(
+			array(
+				'name'       => 'gsheets-no-cred-backend',
+				'base_url'   => 'https://sheets.googleapis.com/v4/spreadsheets',
+				'credential' => 'non-existent-credential',
+				'headers'    => array(),
+			)
+		);
+
+		$addon    = Addon::addon( 'gsheets' );
+		$response = $addon->ping( 'gsheets-no-cred-backend' );
+
+		$this->assertFalse( $response );
+	}
+
+	/**
+	 * Test addon fetch method (list spreadsheets).
+	 */
+	public function test_addon_fetch() {
+		$addon    = Addon::addon( 'gsheets' );
+		$response = $addon->fetch( '', 'gsheets-test-backend' );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+		$this->assertArrayHasKey( 'files', $response['data'] );
+		$this->assertNotEmpty( $response['data']['files'] );
+	}
+
+	/**
+	 * Test addon get_endpoint_schema method for POST.
+	 */
+	public function test_addon_get_endpoint_schema_post() {
+		// First create a bridge so it can be found by get_endpoint_schema.
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-schema-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		// Register the bridge temporarily.
+		$bridges = array( $bridge );
+		tests_add_filter(
+			'forms_bridge_bridges',
+			function ( $existing_bridges, $addon ) use ( $bridges ) {
+				if ( 'gsheets' === $addon ) {
+					return $bridges;
+				}
+
+				return $existing_bridges;
+			},
+			10,
+			2
+		);
+
+		$addon  = Addon::addon( 'gsheets' );
+		$schema = $addon->get_endpoint_schema(
+			'/' . self::SPREADSHEET_ID,
+			'gsheets-test-backend',
+			'POST'
+		);
+
+		$this->assertIsArray( $schema );
+		$this->assertNotEmpty( $schema );
+
+		$field_names = array_column( $schema, 'name' );
+		$this->assertContains( 'Name', $field_names );
+		$this->assertContains( 'Email', $field_names );
+		$this->assertContains( 'Phone', $field_names );
+		$this->assertContains( 'Company', $field_names );
+	}
+
+	/**
+	 * Test addon get_endpoint_schema method for GET returns empty.
+	 */
+	public function test_addon_get_endpoint_schema_get() {
+		$addon  = Addon::addon( 'gsheets' );
+		$schema = $addon->get_endpoint_schema(
+			'/' . self::SPREADSHEET_ID,
+			'gsheets-test-backend',
+			'GET'
+		);
+
+		$this->assertIsArray( $schema );
+		$this->assertEmpty( $schema );
+	}
+
+	/**
+	 * Test appending with partial data (missing columns).
+	 */
+	public function test_append_partial_data() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-partial-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$payload = array(
+			'Name'  => 'Partial User',
+			'Email' => 'partial@example.coop',
+			// Missing Phone and Company.
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
+
+	/**
+	 * Test appending with extra fields not in headers.
+	 */
+	public function test_append_extra_fields() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-extra-fields-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$payload = array(
+			'Name'       => 'Extra User',
+			'Email'      => 'extra@example.coop',
+			'Phone'      => '555-0000',
+			'Company'    => 'Extra Corp',
+			'ExtraField' => 'This should be ignored',
+			'Another'    => 'Also ignored',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
+
+	/**
+	 * Test empty payload handling.
+	 */
+	public function test_empty_payload() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-empty-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$response = $bridge->submit( array() );
+
+		$this->assertFalse( is_wp_error( $response ) );
+	}
+
+	/**
+	 * Test case-insensitive sheet name matching.
+	 */
+	public function test_case_insensitive_sheet_name() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-case-insensitive-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'CONTACTS',
+			)
+		);
+
+		$payload = array(
+			'Name'  => 'Case Test',
+			'Email' => 'case@example.coop',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+	}
+
+	/**
+	 * Test PUT method (should work like POST).
+	 */
+	public function test_put_method() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-put-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'PUT',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$payload = array(
+			'Name'    => 'PUT User',
+			'Email'   => 'put@example.coop',
+			'Phone'   => '555-1111',
+			'Company' => 'PUT Corp',
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
+
+	/**
+	 * Test complex nested structure flattening.
+	 */
+	public function test_complex_nested_flattening() {
+		$bridge = new GSheets_Form_Bridge(
+			array(
+				'name'     => 'test-complex-bridge',
+				'backend'  => 'gsheets-test-backend',
+				'endpoint' => '/' . self::SPREADSHEET_ID,
+				'method'   => 'POST',
+				'tab'      => 'Contacts',
+			)
+		);
+
+		$payload = array(
+			'Name'     => 'Complex User',
+			'Email'    => 'complex@example.coop',
+			'Metadata' => array(
+				'Source'   => 'Web Form',
+				'Campaign' => array(
+					'Name' => 'Spring 2024',
+					'Type' => 'Email',
+				),
+				'Tags'     => array( 'lead', 'qualified' ),
+			),
+		);
+
+		$response = $bridge->submit( $payload );
+
+		$this->assertFalse( is_wp_error( $response ) );
+		$this->assertArrayHasKey( 'data', $response );
+	}
 }
diff --git a/tests/addons/test-vtiger.php b/tests/addons/test-vtiger.php
index 4ab3a6e4..2c910bdc 100644
--- a/tests/addons/test-vtiger.php
+++ b/tests/addons/test-vtiger.php
@@ -265,13 +265,13 @@ private static function get_mock_response( $operation, $query, $body ) {
 							'id'        => '4x11',
 							'firstname' => 'John',
 							'lastname'  => 'Doe',
-							'email'     => 'john.doe@example.com',
+							'email'     => 'john.doe@example.coop',
 						),
 						array(
 							'id'        => '4x12',
 							'firstname' => 'Jane',
 							'lastname'  => 'Smith',
-							'email'     => 'jane.smith@example.com',
+							'email'     => 'jane.smith@example.coop',
 						),
 					),
 				);
@@ -283,7 +283,7 @@ private static function get_mock_response( $operation, $query, $body ) {
 						'id'        => '4x11',
 						'firstname' => 'John',
 						'lastname'  => 'Doe',
-						'email'     => 'john.doe@example.com',
+						'email'     => 'john.doe@example.coop',
 						'phone'     => '555-1234',
 					),
 				);
@@ -546,7 +546,7 @@ public function test_create() {
 		$payload = array(
 			'firstname' => 'John',
 			'lastname'  => 'Doe',
-			'email'     => 'john.doe@example.com',
+			'email'     => 'john.doe@example.coop',
 		);
 
 		$response = $bridge->submit( $payload );