Final answer:
Real-time applications add the element of performance to the testing mix.
Step-by-step explanation:
One of the elements that real-time applications add to the testing mix is performance. Real-time applications are designed to process and respond to events in a timely manner, so testing their performance to ensure they meet the required speed and responsiveness is essential. For example, a real-time application used in online gaming needs to respond quickly to user actions to provide a smooth experience.