Drupal 6 to Drupal 7 - table already exists error

I have module in drupal 6 and try to convert that to drupal 7.

In Drupal 6 the test.install file have

function test_schema(){
$schema = array();

$schema['test_table'] = array(
'description' => 'test table',
'fields' => array(
'id'=>array(
'description' => 'id field',
'type' => 'serial',
'not null' => TRUE
),
'name' => array(
'description' => 'name of user',
'type'=>'varchar',
'length'=>30

)

);
);
}

function test_install()
{
drupal_install_schema('test_schema');
}
function test_uninstall()
{
drupal_uninstall_schema('test_schema');
}

When I place the same module in drupal 7 and install, I got DatabaseSchemaObjectExistsException: Table test_table already exists. in DatabaseSchema->createTable() (line 657 of /includes/database/schema.inc).

From https://drupal.org/update/modules/6/7#update_php understood
_install and _uninstall functions need not to be written in drupal 7. only modulename_schema function is enough and drupal 7 will do install and uninstall automatically.