function test( v ) {
	if ( indexOf( ORIENTATIONS, v ) === -1 ) {
		return new TypeError( format( 'invalid assignment. `%s` must be one of the following: "%s". Value: `%s`.', 'orientation', ORIENTATIONS.join( '", "' ), v ) );
	}
	return null;
}
Validates `orientation`.

@private
@param {*} v - value to test
@returns {(Error|null)} error object or null