Most older personality tests in wide circulation today have significant problems in predicting behavior in meaningful ways (more on that here). Fortunately, the scientific study of personality has made huge strides in recent decades, employing better research methods to obtain more reliable and valid measures. Today, a majority of scientific research on personality focuses on the Five Factor Model because it has proven to be so empirically robust. This model has been painstakingly built on thousands of samples using diverse methods and scales across more than 50 cultures over the last 50 years. Here is one resource to learn more.