my attempt at creating an appointment setting application

How can I ensure that my code, program, or software is functional and secure? Now that I have a firm understanding of software testing and automation, I can write my code more cleanly and ensure the correctness of the functionality of my application/program by practicing testing my projects early on in the development lifecycle; In doing just that, commonly overlooked defects and other bugs within the system can be caught early on reducing the overall cost to make the project a polish product.

How do I interpret user needs and incorporate them into a program? I ensure that I have the best idea of what the user needs by gathering materials and creating documentation; Furthermore, frequent meetings with the user/customer will certify that requirements are being considered and implemented into the program/application the best way that the team can implement them. Similarly, maintaining the greatest understanding completely what the user/customer is asking for (no confusion as to what the requirements are) will help to reduce errors made for lack of knowing how the customer wants a given feature/functionality.

How do I approach designing software? As I proceed in my developing journey, I will work harder to refine gathering information from the client and creating documents to reference as the development cycle progresses. Maintaining documentation will be good for referencing if an issue similar to a previous issue arises; Then the team has something to base the error off of giving them a great place to start for fixing a defect or related issue within the system.