How to use the etlhelper.db_helper_factory.DB_HELPER_FACTORY.from_db_params function in etlhelper

def test_from_db_params_not_registered():
    """
    Tests helpful error message on attempt to choose unregistered db_params
    type.
    """
    db_params = MagicMock(DbParams)
    db_params.dbtype = 'Not a real type'

    with pytest.raises(ETLHelperHelperError,
                       match=r'Unsupported DbParams.dbtype.*'):
        DB_HELPER_FACTORY.from_db_params(db_params)

def test_from_dbparams(dbtype_keyword, expected_helper):
    """
    Tests correct helper produced given a db params object
    """
    db_params = MagicMock(DbParams)
    db_params.dbtype = dbtype_keyword
    helper = DB_HELPER_FACTORY.from_db_params(db_params)
    assert isinstance(helper, expected_helper)

def test_from_db_params_bad_type():
    with pytest.raises(ETLHelperHelperError,
                       match=r'Expected DbParams-like object.*'):
        DB_HELPER_FACTORY.from_db_params('some string')

def connect(db_params, password_variable=None, **kwargs):
    """
    Return database connection.

    :param db_params: DbParams object or similar with appropriate attributes
    :param password_variable: str, name of environment variable with password
    :param kwargs: connection specific keyword arguments e.g. row_factory
    :return: Connection object
    """
    helper = DB_HELPER_FACTORY.from_db_params(db_params)
    # Helpers will raise ETLHelperConnectionError if connection fails
    conn = helper.connect(db_params, password_variable, **kwargs)
    return conn

def get_connection_string(db_params, password_variable):
    """
    Get a connection string

    :param db_params: DbParams object or similar with appropriate attributes
    :param password_variable: str, name of environment variable with password
    :return: str, Connection string
    """
    helper = DB_HELPER_FACTORY.from_db_params(db_params)
    return helper.get_connection_string(db_params, password_variable)

def get_sqlalchemy_connection_string(db_params, password_variable):
    """
    Get a SQLAlchemy connection string.

    :param db_params: DbParams object or similar with appropriate attributes
    :param password_variable: str, name of environment variable with password
    :return: str, Connection string
    """
    helper = DB_HELPER_FACTORY.from_db_params(db_params)
    return helper.get_sqlalchemy_connection_string(db_params, password_variable)