They use some techniques to ensure it. One of the most common methods is by hiring independent third-party auditors. They conduct testing and monitoring of their software and systems. These auditors use various testing methods such as including mathematical algorithms and statistical analysis to ensure that the games are producing random and impartial outcomes. In addition, these casinos also use certain technologies such as random number generators (RNGs) to ensure fair play. RNGs are computer programs that generate random numbers without any predictable patterns. Which ensures that the outcome of the game is completely unpredictable and unbiased. Casinos also use surveillance systems to monitor the games for cheating or fraudulent behavior.