Program Testing and Debugging
Mack Altman III
Capella University
Author Note
This paper is being submitted on April 27, 2015, for Azad Ali’s IT-FP2240 Introduction to Programming course.
Program Testing and Debugging
Introduction
The purpose of this document is to present a detailed description of the Mortgage Calculator. It will explain the application requirements, methods of handling errors within the application, and how to involve the client during the application assessment process. While the application is basic in nature, the application provides an example of work performed to establish the capabilities of its author to utilize error handling within an application.
Application Requirements
The only functional requirement of the application is to prompt the user to supply the user with their potential monthly mortgage payment. The payment should be determined by utilizing the mortgage amount, the down payment made, rate of interest on the proposed mortgage, and term of the mortgage in years. This information should be supplied by the user through prompts upon the execution of the application. In regards to non-functional requirements, the application requires the use of the stdio, math, and errno C libraries.
Application Review
Upon the initial execution of the application, all potential entries are initialized as float in case the user may provide a non-integer numerical value. Upon initial design, these were established as integers until the rate value was encountered. At that time, the values were modified to floating values. Immediately following the initialization of these values, the user is prompted with an introduction to advise the name and purpose of the application.
After the introduction, the user is prompted to enter the potential mortgage amount, down payment, interest rate, and mortgage period in years. A while() loop is used to handle each entry to ensure the user enters usable input. For example, the while() loop for the amount is initialized and will only be exited upon the amount variable being set to something aside from zero (Figure 1). The amount variable is different from the amountIn variable, which is utilized as the user’s input. The usage of the amount variable is within the application and prevents the user’s input from causing issues with the application until it is deemed usable.
Error handling is utilized each time the user enters input by utilizing different methods. While all errors could utilize one method of delivering an error, various methods were utilize to provide use case examples. In Figure 1, the fprintf() function is utilized for displaying a custom message to the user while providing the errno in parentheses. The perror() function is utilized in Figure 2 to handle the user’s input for the down payment. The error handling for the interest rate is handled a little differently than the mortgage amount by providing the string associated with the errno instead of the errno itself. This is illustrated in Figure 3. The resulting output of each of these error handlers can be seen in Figure 4.
Application Assessment
Despite the simplicity of the application, a client will always require they be involved at some point within the development lifecycle. Additionally, the involvement of the client will minimize tangents which many developers find themselves on in trying to identify ‘what the client really wants’ as opposed to ‘what the client said they wanted’. Prior to development, a meeting with the client should determine the initial requirements. After the initial application is developed and obvious errors have been removed, an additional meeting should be made to ensure all of the initial requirements have been met while bringing to the client’s attention modifications that may have been made along the way. After all deliverables have been made and a period of time has passed, there should be another meeting with the client to ensure the application is working as they had desired. This last meeting does not always occur due to change management not being a priority; however, this is an effective method of ensuring the client is satisfied and in some cases can provide profitable opportunities as the client may want something else for the application or bring up a different project the developers can assist with.
Conclusion
While there may be many methods for handling errors, there are various approaches that are made as to why one may be used over another. Some developers may feel error codes should not be displayed as the user is provided with no use; however, more technical developers may feel the error code is necessary due to the user being able to provide the error code to the developer and easing the identification of the error encountered. In the end, it will be determined by the design and development team to make these decisions for the application. Due to the limitless possibilities, the developer should have some familiarity with each approach.

Figures

Figure 1. Example of while() loop being utilized to handle user’s input for the mortgage amount.

Figure 2. Example of while() loop being utilized to handle user’s input for the down payment.

Figure 3. Example of while() loop being utilized to handle user’s input for the interest rate

Figure 4. Example of the mortgage calculator being ran and executing with each various error handler in use.