Atomic Spin :: Elements of Software

We’re working on adding significant new functionality to a legacy system. The budget doesn’t support a complete re-write. None of the legacy code has tests. The application domain is automotive testing. The particular problem at hand is controlling a throttle actuator (a simple robot that activates the throttle of a car while it’s being tested.)

The challenge

Legacy C source, 1600 lines. Many authors, 15+ years old. Complex if/else logic blocks with multiple clauses in conditionals. Several global variables. Throttle commands sent out serial port. Shared memory global variables via CPP macro interface.

How to add functionality in a TDD fashion for moving the robot smoothly?