Code Driven Testing

A growing trend in software development is the use of xUnit testing frameworks JUnit, NUnit, PhpUnit, etc. they allow unit tests executions to test specific code scenarios and sections. It can also help on testing code API with few argument options.

Test cases describe test scenarios that need to be verify to make sure the program runs as expected and according to its requirements. Code Drive Testing, and code driven test automation is a key feature of Agile software development practice. 

Code drive testing also know as Test Driven Development (TDD).

The TDD best practice means writing the unit test to define its functionality and aim before implementing it by code, so the moment the test pass means the code is ready.

Proponents argue that it produces software that is both more reliable and less costly than code that is tested by manual exploration. It is considered more reliable because the code coverage is better, and because it is run constantly during development rather than once at the end of a waterfall development cycle.
The developer discovers defects immediately upon making a change, when it is least expensive to fix, which make the all process much more faster and safer, transforming the code into a simpler form with less code duplication, but equivalent behavior, and with on going tests, which can be repeatedly executed, making the overall release much more safer from new defects.