1.2. The need for a testing framework
The first level of testing comes from you. When you implement a new feature, you make a small code change and then run the application to see whether the required functionality is ready. Compiling and running your code is a daily task that happens many times a day as you progress toward the required functionality.
Some features, such as “add a button here that sorts this table of the report,” are trivial enough that they can be implemented and tested in one run. But more-complex features, such as “we need to change the policy of approving/rejecting a loan,” will need several changes and runs of the application until the feature is marked as complete.
You can see this manual code-run-verify cycle in figure ...