Your cyber security is only as strong as its biggest vulnerability!
How do you test the effectiveness of your security? Try to break through it of course. Malicious users will stop at nothing to get to your data. The best way for you to adequately prepare for what they are going to throw at you, is to do it to yourself.
Hackers look for vulnerabilities in your system and try to exploit them. Being able to find those vulnerabilities yourself, and successfully patch them before they can be exploited, will go a long way towards bolstering your defenses.