Unit testing and the reason for mocking
If you’ve read my definitions of unit testing and system testing in my Ten Tenets of Test Automation, you’ll know that the primary differences between the two are target audience and granularity of coverage. Unit tests seek to validate the intentions of developers at a very fine, narrow scope, often at the function or small class level.
There should be lots of these fine-grained checks to validate your code base. Having them helps you understand the impact of evolving requirements. Having to deal with change in the life of developing a product is as certain as