You should unit-test everything, of course. However, you also need to make sure you don't omit anything from testing and ensure that you're testing your classes in the correct manner. The following IEEE standards are intended for software quality, including testing and verification:
The IEEE standard 1008-1987, "Standard for Software Unit Testing" (http://standards.ieee.org/reading/ieee/std_public/description/se/), provides a helpful overview of how you should test your application. It has the following outline:
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