01. Introduction and Goals

What is the Mars Rover Kata?

The Mars Rover Kata is a classic software design exercise. A rover is deployed onto a rectangular plateau on Mars. An operator sends it a sequence of commands — turn left (L), turn right (R), or move forward (M). The rover must navigate the grid, maintain its position and orientation, and never leave the plateau. An optional extension adds obstacle detection.

The kata is small enough to implement in an afternoon, but rich enough to practice clean architecture, domain modelling, and test-driven development.

Functional Requirements

ID

Requirement

FR-1

The system accepts a plateau size defined by its upper-right corner coordinates (e.g. 5 5); the lower-left corner is always 0 0

FR-2

The system accepts one or more rovers, each with an initial position (x, y) and a cardinal heading (N, E, S, W)

FR-3

Each rover receives a command string composed of: L (turn left 90°), R (turn right 90°), M (move one step forward)

FR-4

Rovers are processed sequentially — a rover completes all its commands before the next one starts

FR-5

The system reports the final position and heading of every rover

FR-6

A rover must not move outside the plateau boundaries

FR-7

(Optional) The system detects obstacles on the plateau; a rover stops before hitting one and reports its last safe position

Quality Goals

Priority

Quality Goal

Scenario

1

Correctness

Given any valid input, the system always produces the correct final positions

2

Safety

A rover never moves to an invalid position (out of bounds or occupied by an obstacle)

3

Testability

All domain rules are exercisable through unit tests with no I/O setup required

4

Extensibility

New command types or movement strategies can be added without modifying existing domain logic

5

Readability

The code structure reflects the domain language — Rover, Plateau, Heading, Command

Stakeholders

Stakeholder

Interest

Operator

Issue commands and receive accurate final rover positions

Developer

A clean, well-structured codebase that is easy to extend and test

Course Student

Understand how arc42 and C4 apply to a real (if small) system