From 9da928c819413d2ee66a1e87c67f9f8e9ee17ac2 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 12:56:14 +0100
Subject: [PATCH 01/54] Introduce kata and summarise the steps

---
 test-pnpm/mars_rovers/README.md     | 159 ++++++++++++++++++++++++++++
 test-pnpm/morning_routine/README.md |   0
 2 files changed, 159 insertions(+)
 create mode 100644 test-pnpm/mars_rovers/README.md
 delete mode 100644 test-pnpm/morning_routine/README.md

diff --git a/test-pnpm/mars_rovers/README.md b/test-pnpm/mars_rovers/README.md
new file mode 100644
index 0000000..01383d5
--- /dev/null
+++ b/test-pnpm/mars_rovers/README.md
@@ -0,0 +1,159 @@
+## Instructions
+
+A squad of robotic rovers are to be landed by NASA on a plateau on Mars.
+
+This plateau, which is curiously rectangular, must be navigated by the rovers so that their onboard cameras can get a complete view of the surrounding terrain to send back to Earth.
+
+Your task is to develop an API that moves the rovers around on the plateau.
+
+In this API, the plateau is represented as a 10x10 grid, and a rover has state consisting of two parts:
+
+- its position on the grid (represented by an X,Y coordinate pair)
+- the compass direction it's facing (represented by a letter, one of `N`, `S`, `E`, `W`)
+
+### Input
+
+The input to the program is a string of one-character move commands:
+
+- `L` and `R` rotate the direction the rover is facing
+- `M` moves the rover one grid square forward in the direction it is currently facing
+
+If a rover reaches the end of the plateau, it wraps around the end of the grid.
+
+### Output
+
+The program's output is the final position of the rover after all the move commands have been executed. The position is represented as a coordinate pair and a direction, joined by colons to form a string. For example: a rover whose position is `2:3:W` is at square (2,3), facing west.
+
+### Obstacles
+
+The grid may have obstacles. If a given sequence of commands encounters an obstacle, the rover moves up to the last possible point and reports the obstacle by prefixing `O:` to the position string that it returns. For instance, `O:1:1:N` would mean that the rover encountered an obstacle at position (1, 2).
+
+### Examples
+
+- given a grid with no obstacles, input `MMRMMLM` gives output `2:3:N`
+- given a grid with no obstacles, input `MMMMMMMMMM` gives output `0:0:N` (due to wrap-around)
+- given a grid with an obstacle at (0, 3), input `MMMM` gives output `O:0:2:N`
+
+### Interface
+
+There are no restrictions on the design of the public interface. In particular, much of the details of the obstacle feature's implementation are up to you.
+
+Rules:
+
+- The rover receives a char array of commands e.g. `RMMLM` and returns the finishing point after the moves e.g. `2:1:N`
+- The rover wraps around if it reaches the end of the grid.
+
+Credit: [Google Code Archive](https://code.google.com/archive/p/marsrovertechchallenge/)
+
+Credit: [Google Code Archive](https://code.google.com/archive/p/marsrovertechchallenge/)
+
+## Useful Links
+
+### Books
+
+- [Head First Design Patterns](https://www.oreilly.com/library/view/head-first-design/0596007124/) by Eric Freeman et al.
+- [Understanding the Four Rules of Simple Design](https://leanpub.com/4rulesofsimpledesign) by Corey Haines
+
+### Articles
+
+- [Mars Rover Kata: Refactoring to Patterns](https://codurance.com/2019/01/22/mars-rover-kata-refactoring-to-patterns/) by [Simion Iulian Belea](https://codurance.com/publications/author/simion-iulian-belea/)
+
+### Solutions
+
+- [Java](https://github.com/sandromancuso/mars-rover-screencast/tree/screencast) by[ Sandro Mancuso](https://www.codurance.com/publications/author/sandro-mancuso) 
+
+## Steps
+
+Certainly, Vincent. Here's a well-structured summary of steps to break down the Mars Rover kata into focused, testable iterations using outside-in TDD. This progression balances incremental delivery, testability, and clean design principles:
+
+------
+
+## ✅ Step-by-Step Breakdown for the Mars Rover Kata (TypeScript)
+
+### 🧭 **1. Define the Domain Types and Enums**
+
+- **Purpose**: Model the rover’s state and commands.
+- **Entities**:
+  - `Direction` enum or type union: `'N' | 'E' | 'S' | 'W'`
+  - `Position` type: `{ x: number; y: number }`
+  - `Command` type: `'L' | 'R' | 'M'`
+
+✅ Write unit tests for parsing and wrapping directions if you prefer utility functions early.
+
+------
+
+### 🧱 **2. Implement the `Grid`**
+
+- **Responsibility**: Represent a 10x10 plateau, handle wrap-around logic, and detect obstacles.
+- **Features**:
+  - `wrap(position: Position): Position`
+  - `hasObstacle(position: Position): boolean`
+
+✅ Unit tests:
+
+- `wrap({x:10,y:0}) => {x:0,y:0}`
+- `hasObstacle({x:0,y:3}) => true`
+
+------
+
+### 🚙 **3. Create the `MarsRover` Class Skeleton**
+
+- **Initial state**: Position at (0, 0), facing North
+
+✅ Unit test:
+
+- `new MarsRover(grid).execute('') => '0:0:N'`
+
+------
+
+### 🔁 **4. Implement Turning Logic**
+
+- `L` and `R` commands modify direction
+- Use direction index rotation: N → E → S → W → N
+
+✅ Unit tests:
+
+- `'L' from N => W`
+- `'R' from N => E`
+
+------
+
+### ➡️ **5. Implement Forward Movement (`M`)**
+
+- Move one step in the direction facing
+- Use `Grid.wrap()` to handle edge crossing
+
+✅ Unit tests:
+
+- `execute('M')` updates position to `0:1:N`
+- `execute('MMMMMMMMMM')` wraps to `0:0:N`
+
+------
+
+### ⛰️ **6. Add Obstacle Handling**
+
+- Prevent movement into an obstacle
+- Prefix output with `O:` and report last safe position
+
+✅ Unit tests:
+
+- Obstacle at `0:3`, `execute('MMMM') => O:0:2:N`
+
+------
+
+### 🧪 **7. Full Behavioural Tests**
+
+Add scenario-based tests:
+
+- `MMRMMLM => 2:3:N`
+- `MMMMMMMMMM => 0:0:N`
+- `MMMM` with obstacle at `0:3 => O:0:2:N`
+
+------
+
+### 🧼 **8. Refactor & Polish**
+
+- Extract reusable logic (e.g. `rotate`, `nextPosition`)
+- Add immutability if you favour a purer style
+- Optionally expose state inspection for diagnostics/logging
+
diff --git a/test-pnpm/morning_routine/README.md b/test-pnpm/morning_routine/README.md
deleted file mode 100644
index e69de29..0000000

From 9d79199afb804766fe93de920eb1cef8499b7970 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 13:08:52 +0100
Subject: [PATCH 02/54] Add failing test for getting started

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 test-pnpm/mars_rovers/mars.rover.should.test.ts

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
new file mode 100644
index 0000000..58099e7
--- /dev/null
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -0,0 +1,9 @@
+describe('mars rover should', () => {
+  test('report its default start position', () => {
+    let marsRover = new MarsRover();
+
+    const actual = marsRover.Execute('');
+
+    expect(actual).toBe('0:0:N');
+  });
+});

From ee76f413baae123540a79e55d0a7f31945adbbc4 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 13:11:50 +0100
Subject: [PATCH 03/54] Make simple test pass

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 58099e7..f128ca2 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -2,8 +2,14 @@ describe('mars rover should', () => {
   test('report its default start position', () => {
     let marsRover = new MarsRover();
 
-    const actual = marsRover.Execute('');
+    const actual = marsRover.execute('');
 
     expect(actual).toBe('0:0:N');
   });
 });
+
+export class MarsRover {
+  execute(command: string): string {
+    return '0:0:N';
+  }
+}

From 9db2ac8e3947833e09c85914cf6f3e3cf42200ce Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 13:15:26 +0100
Subject: [PATCH 04/54] Refactor moving the sut into its own file

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 8 ++------
 test-pnpm/mars_rovers/mars.rover.ts             | 5 +++++
 2 files changed, 7 insertions(+), 6 deletions(-)
 create mode 100644 test-pnpm/mars_rovers/mars.rover.ts

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index f128ca2..dcc34eb 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -1,3 +1,5 @@
+import { MarsRover } from './mars.rover';
+
 describe('mars rover should', () => {
   test('report its default start position', () => {
     let marsRover = new MarsRover();
@@ -7,9 +9,3 @@ describe('mars rover should', () => {
     expect(actual).toBe('0:0:N');
   });
 });
-
-export class MarsRover {
-  execute(command: string): string {
-    return '0:0:N';
-  }
-}
diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
new file mode 100644
index 0000000..fa41d34
--- /dev/null
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -0,0 +1,5 @@
+export class MarsRover {
+  execute(command: string): string {
+    return '0:0:N';
+  }
+}

From 5e57507b2dfc30071f131cfbe86557c3e70cace1 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 13:25:00 +0100
Subject: [PATCH 05/54] (RED) Create failing test for a single move in the same
 direction

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index dcc34eb..7b7282b 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -8,4 +8,12 @@ describe('mars rover should', () => {
 
     expect(actual).toBe('0:0:N');
   });
+
+  test('move in the same direction with single move command', () => {
+    let marsRover = new MarsRover();
+
+    const actual = marsRover.execute('M');
+
+    expect(actual).toBe('0:1:N');
+  });
 });

From 542a0a67be6e39e1b75c9ab1372533dda3309a55 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 13:32:42 +0100
Subject: [PATCH 06/54] (GREEN) make test pass for single move in the same
 direction

---
 test-pnpm/mars_rovers/mars.rover.ts | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index fa41d34..046398c 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -1,5 +1,8 @@
 export class MarsRover {
   execute(command: string): string {
+    if (command === 'M') {
+      return '0:1:N';
+    }
     return '0:0:N';
   }
 }

From c7abf41d9d6dcfa505c284483d800bc19992265c Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 13:42:30 +0100
Subject: [PATCH 07/54] (GREEN) Refactor test and remove duplication

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 7b7282b..5164695 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -1,17 +1,19 @@
 import { MarsRover } from './mars.rover';
 
 describe('mars rover should', () => {
-  test('report its default start position', () => {
-    let marsRover = new MarsRover();
+  let marsRover: MarsRover;
+
+  beforeEach(() => {
+    marsRover = new MarsRover();
+  });
 
+  test('report its default start position', () => {
     const actual = marsRover.execute('');
 
     expect(actual).toBe('0:0:N');
   });
 
-  test('move in the same direction with single move command', () => {
-    let marsRover = new MarsRover();
-
+  test('move in the same direction with a single move command', () => {
     const actual = marsRover.execute('M');
 
     expect(actual).toBe('0:1:N');

From 630012754725519e69d00d3d3b7b5cb0eb62c981 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 13:49:19 +0100
Subject: [PATCH 08/54] (RED) change direction

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 5164695..1270182 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -18,4 +18,10 @@ describe('mars rover should', () => {
 
     expect(actual).toBe('0:1:N');
   });
+
+  test('turn right facing east', () => {
+    const actual = marsRover.execute('R');
+
+    expect(actual).toBe('0:0:E');
+  });
 });

From c2713f9ff1069f02544d12203589c1db55e80ad9 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 13:51:56 +0100
Subject: [PATCH 09/54] (GREEN) pass change direction

---
 test-pnpm/mars_rovers/mars.rover.ts | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 046398c..274c686 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -3,6 +3,9 @@ export class MarsRover {
     if (command === 'M') {
       return '0:1:N';
     }
+    if (command === 'R') {
+      return '0:0:E';
+    }
     return '0:0:N';
   }
 }

From 33e954e9b1660ede065b1eb316d19160d1a352cd Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 14:19:08 +0100
Subject: [PATCH 10/54] (REF) Introduce basic variables used simply in
 interpolation strings

---
 test-pnpm/mars_rovers/mars.rover.ts | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 274c686..7df82bd 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -1,11 +1,15 @@
 export class MarsRover {
+  private _direction: 'N' | 'E' | 'S' | 'W' = 'N';
+  private _x: number = 0;
+  private _y: number = 0;
+
   execute(command: string): string {
     if (command === 'M') {
-      return '0:1:N';
+      return `${this._x}:${this._y + 1}:${this._direction}`;
     }
     if (command === 'R') {
-      return '0:0:E';
+      return `${this._x}:${this._y}:E`;
     }
-    return '0:0:N';
+    return `${this._x}:${this._y}:${this._direction}`;
   }
 }

From 42fbfefdbcb74623391c787303e8e8b337702125 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 14:34:49 +0100
Subject: [PATCH 11/54] (RED) Failing test to expand commands in the same
 direction

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 1270182..68640f1 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -19,9 +19,21 @@ describe('mars rover should', () => {
     expect(actual).toBe('0:1:N');
   });
 
+  test('move in the same direction with a single move command', () => {
+    const actual = marsRover.execute('M');
+
+    expect(actual).toBe('0:1:N');
+  });
+
   test('turn right facing east', () => {
     const actual = marsRover.execute('R');
 
     expect(actual).toBe('0:0:E');
   });
+
+  test('move in the same direction with a double move command', () => {
+    const actual = marsRover.execute('MM');
+
+    expect(actual).toBe('0:2:N');
+  });
 });

From 29acb7dd474bfa43884cf12cedacc67f74017d83 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 14:40:10 +0100
Subject: [PATCH 12/54] (GREEN) Iterate through commands making smallest change

---
 test-pnpm/mars_rovers/mars.rover.ts | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 7df82bd..4d03351 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -3,12 +3,14 @@ export class MarsRover {
   private _x: number = 0;
   private _y: number = 0;
 
-  execute(command: string): string {
-    if (command === 'M') {
-      return `${this._x}:${this._y + 1}:${this._direction}`;
-    }
-    if (command === 'R') {
-      return `${this._x}:${this._y}:E`;
+  execute(commands: string): string {
+    for (const command of commands) {
+      if (command === 'M') {
+        this._y = this._y + 1;
+      }
+      if (command === 'R') {
+        this._direction = 'E';
+      }
     }
     return `${this._x}:${this._y}:${this._direction}`;
   }

From b71f641f753f134c6626f9c1e2163960890144d3 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 14:54:25 +0100
Subject: [PATCH 13/54] (REFACTOR) Extract human readable types and enums

---
 .../mars_rovers/mars.rover.should.test.ts     |  6 -----
 test-pnpm/mars_rovers/mars.rover.ts           | 26 ++++++++++++++++---
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 68640f1..5a87371 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -19,12 +19,6 @@ describe('mars rover should', () => {
     expect(actual).toBe('0:1:N');
   });
 
-  test('move in the same direction with a single move command', () => {
-    const actual = marsRover.execute('M');
-
-    expect(actual).toBe('0:1:N');
-  });
-
   test('turn right facing east', () => {
     const actual = marsRover.execute('R');
 
diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 4d03351..8ea9201 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -1,15 +1,33 @@
+type Direction =
+  | DirectionType.North
+  | DirectionType.East
+  | DirectionType.South
+  | DirectionType.West;
+
+enum DirectionType {
+  North = 'N',
+  East = 'E',
+  South = 'S',
+  West = 'W',
+}
+
+enum CommandType {
+  Move = 'M',
+  TurnRight = 'R',
+}
+
 export class MarsRover {
-  private _direction: 'N' | 'E' | 'S' | 'W' = 'N';
+  private _direction: Direction = DirectionType.North;
   private _x: number = 0;
   private _y: number = 0;
 
   execute(commands: string): string {
     for (const command of commands) {
-      if (command === 'M') {
+      if (command === CommandType.Move) {
         this._y = this._y + 1;
       }
-      if (command === 'R') {
-        this._direction = 'E';
+      if (command === CommandType.TurnRight) {
+        this._direction = DirectionType.East;
       }
     }
     return `${this._x}:${this._y}:${this._direction}`;

From d82ca6fd41226e6813142d77da40ed715a09b9ed Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 15:06:55 +0100
Subject: [PATCH 14/54] (RED) Failing test for continually changing direction

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 5a87371..64a96cb 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -25,6 +25,12 @@ describe('mars rover should', () => {
     expect(actual).toBe('0:0:E');
   });
 
+  test('turn right twice facing south', () => {
+    const actual = marsRover.execute('RR');
+
+    expect(actual).toBe('0:0:S');
+  });
+
   test('move in the same direction with a double move command', () => {
     const actual = marsRover.execute('MM');
 

From 4da7bafa81c7f424cd84feb0983fe5997bcbaf0f Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 15:20:12 +0100
Subject: [PATCH 15/54] (GREEN) Fix incremental direction change

---
 test-pnpm/mars_rovers/mars.rover.ts | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 8ea9201..a50d014 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -18,6 +18,13 @@ enum CommandType {
 
 export class MarsRover {
   private _direction: Direction = DirectionType.North;
+  private _directions: Direction[] = new Array<Direction>(
+    DirectionType.North,
+    DirectionType.East,
+    DirectionType.South,
+    DirectionType.West,
+  );
+  private _directionIndex = 0;
   private _x: number = 0;
   private _y: number = 0;
 
@@ -27,9 +34,9 @@ export class MarsRover {
         this._y = this._y + 1;
       }
       if (command === CommandType.TurnRight) {
-        this._direction = DirectionType.East;
+        this._directionIndex = this._directionIndex + 1;
       }
     }
-    return `${this._x}:${this._y}:${this._direction}`;
+    return `${this._x}:${this._y}:${this._directions[this._directionIndex]}`;
   }
 }

From 722bd884806cddd40a9d48598b2fd12085e59641 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 15:21:40 +0100
Subject: [PATCH 16/54] (REFACTOR): Remove unused variable

---
 test-pnpm/mars_rovers/mars.rover.ts | 1 -
 1 file changed, 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index a50d014..e0dd8f8 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -17,7 +17,6 @@ enum CommandType {
 }
 
 export class MarsRover {
-  private _direction: Direction = DirectionType.North;
   private _directions: Direction[] = new Array<Direction>(
     DirectionType.North,
     DirectionType.East,

From 6ad42fbe63ef93e382f5745cc2c66ae8ce4851bf Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 15:25:22 +0100
Subject: [PATCH 17/54] (RED) Failing test for turning to face north again

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 64a96cb..2f4eb3b 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -31,6 +31,12 @@ describe('mars rover should', () => {
     expect(actual).toBe('0:0:S');
   });
 
+  test('turn right 4 times and face north again', () => {
+    const actual = marsRover.execute('RRRR');
+
+    expect(actual).toBe('0:0:N');
+  });
+
   test('move in the same direction with a double move command', () => {
     const actual = marsRover.execute('MM');
 

From 46964fddc7936db0b0319d7abfd077d322f2e280 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 15:28:09 +0100
Subject: [PATCH 18/54] (GREEN) Implement simple cardinality to bring it back
 in the correct direction

---
 test-pnpm/mars_rovers/mars.rover.ts | 32 +++++++++++++++++++----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index e0dd8f8..8389aeb 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -1,10 +1,10 @@
 type Direction =
-  | DirectionType.North
-  | DirectionType.East
-  | DirectionType.South
-  | DirectionType.West;
+  | CompassDirection.North
+  | CompassDirection.East
+  | CompassDirection.South
+  | CompassDirection.West;
 
-enum DirectionType {
+enum CompassDirection {
   North = 'N',
   East = 'E',
   South = 'S',
@@ -18,10 +18,10 @@ enum CommandType {
 
 export class MarsRover {
   private _directions: Direction[] = new Array<Direction>(
-    DirectionType.North,
-    DirectionType.East,
-    DirectionType.South,
-    DirectionType.West,
+    CompassDirection.North,
+    CompassDirection.East,
+    CompassDirection.South,
+    CompassDirection.West,
   );
   private _directionIndex = 0;
   private _x: number = 0;
@@ -30,12 +30,22 @@ export class MarsRover {
   execute(commands: string): string {
     for (const command of commands) {
       if (command === CommandType.Move) {
-        this._y = this._y + 1;
+        this.moveForward();
       }
+
       if (command === CommandType.TurnRight) {
-        this._directionIndex = this._directionIndex + 1;
+        this.moveRight();
       }
     }
+
     return `${this._x}:${this._y}:${this._directions[this._directionIndex]}`;
   }
+
+  private moveRight() {
+    this._directionIndex = (this._directionIndex + 1) % this._directions.length;
+  }
+
+  private moveForward() {
+    this._y = this._y + 1;
+  }
 }

From f3fa38c3ec29827ecb666d921a92b623cee83808 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 15:47:04 +0100
Subject: [PATCH 19/54] (RED) Failing test for turning left

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 2f4eb3b..3c64ed7 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -37,6 +37,12 @@ describe('mars rover should', () => {
     expect(actual).toBe('0:0:N');
   });
 
+  test('turn left facing west', () => {
+    const actual = marsRover.execute('L');
+
+    expect(actual).toBe('0:0:W');
+  });
+
   test('move in the same direction with a double move command', () => {
     const actual = marsRover.execute('MM');
 

From 9ae336f9cc3bf6b791f8e9b56da7129035a048cf Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 16:00:53 +0100
Subject: [PATCH 20/54] (GREEN) Matched existing moveRight pattern for
 symmmetry extracted currentDirection method to make it more redable

---
 test-pnpm/mars_rovers/mars.rover.ts | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 8389aeb..c51750d 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -14,6 +14,7 @@ enum CompassDirection {
 enum CommandType {
   Move = 'M',
   TurnRight = 'R',
+  TurnLeft = 'L',
 }
 
 export class MarsRover {
@@ -29,16 +30,30 @@ export class MarsRover {
 
   execute(commands: string): string {
     for (const command of commands) {
-      if (command === CommandType.Move) {
-        this.moveForward();
-      }
-
-      if (command === CommandType.TurnRight) {
-        this.moveRight();
+      switch (command) {
+        case CommandType.Move:
+          this.moveForward();
+          break;
+        case CommandType.TurnRight:
+          this.moveRight();
+          break;
+        case CommandType.TurnLeft:
+          this.moveLeft();
+          break;
       }
     }
 
-    return `${this._x}:${this._y}:${this._directions[this._directionIndex]}`;
+    return `${this._x}:${this._y}:${this.currentDirection()}`;
+  }
+
+  private currentDirection(): Direction {
+    return this._directions[this._directionIndex];
+  }
+
+  private moveLeft() {
+    // subtract 1 but wrap around if < 0
+    this._directionIndex =
+      (this._directionIndex - 1 + this._directions.length) % this._directions.length;
   }
 
   private moveRight() {

From 37d53a417d6c6808dc2f8acc07ce41f4cff5bb1c Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 16:50:29 +0100
Subject: [PATCH 21/54] (RED) Failing test for moving north than south

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 3c64ed7..0ae8b83 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -19,6 +19,12 @@ describe('mars rover should', () => {
     expect(actual).toBe('0:1:N');
   });
 
+  test('move forward and then turn facing south', () => {
+    const actual = marsRover.execute('MRRM');
+
+    expect(actual).toBe('0:0:S');
+  });
+
   test('turn right facing east', () => {
     const actual = marsRover.execute('R');
 

From 93f944a8eb9f83e09cc33253e479f9ed082ed51c Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 16:51:14 +0100
Subject: [PATCH 22/54] (GREEN) Fix move to cater for direction

---
 test-pnpm/mars_rovers/mars.rover.ts | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index c51750d..86c3e6d 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -50,17 +50,22 @@ export class MarsRover {
     return this._directions[this._directionIndex];
   }
 
-  private moveLeft() {
+  private moveLeft(): void {
     // subtract 1 but wrap around if < 0
     this._directionIndex =
       (this._directionIndex - 1 + this._directions.length) % this._directions.length;
   }
 
-  private moveRight() {
+  private moveRight(): void {
     this._directionIndex = (this._directionIndex + 1) % this._directions.length;
   }
 
-  private moveForward() {
-    this._y = this._y + 1;
+  private moveForward(): void {
+    if (this.currentDirection() === CompassDirection.North) {
+      this._y = this._y + 1;
+    }
+    if (this.currentDirection() === CompassDirection.South) {
+      this._y = this._y - 1;
+    }
   }
 }

From 2862a79c7962dbb5b2b7aa04ee3678d08352aa60 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 16:54:24 +0100
Subject: [PATCH 23/54] (REFACTOR): Swicth move ifs to case

---
 test-pnpm/mars_rovers/mars.rover.ts | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 86c3e6d..e6b14a8 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -61,11 +61,15 @@ export class MarsRover {
   }
 
   private moveForward(): void {
-    if (this.currentDirection() === CompassDirection.North) {
-      this._y = this._y + 1;
-    }
-    if (this.currentDirection() === CompassDirection.South) {
-      this._y = this._y - 1;
+    switch (this.currentDirection()) {
+      case CompassDirection.North: {
+        this._y = this._y + 1;
+        break;
+      }
+      case CompassDirection.South: {
+        this._y = this._y - 1;
+        break;
+      }
     }
   }
 }

From 9037f023b80dc2f8a9349203e16c1f269f30298d Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 16:57:45 +0100
Subject: [PATCH 24/54] (RED) Add failing test for moving east

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 0ae8b83..00c4f80 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -54,4 +54,10 @@ describe('mars rover should', () => {
 
     expect(actual).toBe('0:2:N');
   });
+
+  test('move forward facing east', () => {
+    const actual = marsRover.execute('RM');
+
+    expect(actual).toBe('1:0:E');
+  });
 });

From 44ebbf57a5e27e6af260c5846f790bdb97bdd990 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 16:58:07 +0100
Subject: [PATCH 25/54] (GREEN) Fix east move test

---
 test-pnpm/mars_rovers/mars.rover.ts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index e6b14a8..2bba6d8 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -70,6 +70,10 @@ export class MarsRover {
         this._y = this._y - 1;
         break;
       }
+      case CompassDirection.East: {
+        this._x = this._x + 1;
+        break;
+      }
     }
   }
 }

From 156942d7eee17fb9a284f686e186d9132a2991cc Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:02:57 +0100
Subject: [PATCH 26/54] (RED) Add failing test for moving west

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 00c4f80..1635136 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -60,4 +60,10 @@ describe('mars rover should', () => {
 
     expect(actual).toBe('1:0:E');
   });
+
+  test('move forward facing west', () => {
+    const actual = marsRover.execute('RMLLM');
+
+    expect(actual).toBe('0:0:W');
+  });
 });

From 8d440cf5f9eb4c1098eff7e4e2c6018f1c800fba Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:03:22 +0100
Subject: [PATCH 27/54] (GREEN) Fix west moving test

---
 test-pnpm/mars_rovers/mars.rover.ts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 2bba6d8..6329ee1 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -74,6 +74,10 @@ export class MarsRover {
         this._x = this._x + 1;
         break;
       }
+      case CompassDirection.West: {
+        this._x = this._x - 1;
+        break;
+      }
     }
   }
 }

From 406248525dfae13a7627d6d5ae32625bba32a2ab Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:06:35 +0100
Subject: [PATCH 28/54] (REFACTOR): Simplify test using test each

---
 .../mars_rovers/mars.rover.should.test.ts     | 73 ++++---------------
 1 file changed, 15 insertions(+), 58 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 1635136..d4ba393 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -7,63 +7,20 @@ describe('mars rover should', () => {
     marsRover = new MarsRover();
   });
 
-  test('report its default start position', () => {
-    const actual = marsRover.execute('');
-
-    expect(actual).toBe('0:0:N');
-  });
-
-  test('move in the same direction with a single move command', () => {
-    const actual = marsRover.execute('M');
-
-    expect(actual).toBe('0:1:N');
-  });
-
-  test('move forward and then turn facing south', () => {
-    const actual = marsRover.execute('MRRM');
-
-    expect(actual).toBe('0:0:S');
-  });
-
-  test('turn right facing east', () => {
-    const actual = marsRover.execute('R');
-
-    expect(actual).toBe('0:0:E');
-  });
-
-  test('turn right twice facing south', () => {
-    const actual = marsRover.execute('RR');
-
-    expect(actual).toBe('0:0:S');
-  });
-
-  test('turn right 4 times and face north again', () => {
-    const actual = marsRover.execute('RRRR');
-
-    expect(actual).toBe('0:0:N');
-  });
-
-  test('turn left facing west', () => {
-    const actual = marsRover.execute('L');
-
-    expect(actual).toBe('0:0:W');
-  });
-
-  test('move in the same direction with a double move command', () => {
-    const actual = marsRover.execute('MM');
-
-    expect(actual).toBe('0:2:N');
-  });
-
-  test('move forward facing east', () => {
-    const actual = marsRover.execute('RM');
-
-    expect(actual).toBe('1:0:E');
-  });
-
-  test('move forward facing west', () => {
-    const actual = marsRover.execute('RMLLM');
-
-    expect(actual).toBe('0:0:W');
+  test.each([
+    ['report its default start position', '', '0:0:N'],
+    ['move in the same direction with a single move command', 'M', '0:1:N'],
+    ['move forward and then turn facing south', 'MRRM', '0:0:S'],
+    ['turn right facing east', 'R', '0:0:E'],
+    ['turn right twice facing south', 'RR', '0:0:S'],
+    ['turn right 4 times and face north again', 'RRRR', '0:0:N'],
+    ['turn left facing west', 'L', '0:0:W'],
+    ['move in the same direction with a double move command', 'MM', '0:2:N'],
+    ['move forward facing east', 'RM', '1:0:E'],
+    ['move forward facing west', 'RMLLM', '0:0:W'],
+  ])('%s', (_, input, expected) => {
+    const actual = marsRover.execute(input);
+
+    expect(actual).toBe(expected);
   });
 });

From 98e626bb8a0398ab29c42191cf3b4ba40d9b6c40 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:17:01 +0100
Subject: [PATCH 29/54] (RED) Add failing test for north to bottom

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index d4ba393..345ab90 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -18,6 +18,7 @@ describe('mars rover should', () => {
     ['move in the same direction with a double move command', 'MM', '0:2:N'],
     ['move forward facing east', 'RM', '1:0:E'],
     ['move forward facing west', 'RMLLM', '0:0:W'],
+    ['wrap around north edge to bottom', 'MMMMMMMMMM', '0:0:N'],
   ])('%s', (_, input, expected) => {
     const actual = marsRover.execute(input);
 

From a4ba99e3a7a4a6c3c88f1162863178028a3704d8 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:17:20 +0100
Subject: [PATCH 30/54] (GREEN) Fix failing  test

---
 test-pnpm/mars_rovers/mars.rover.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 6329ee1..dd56d6c 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -27,6 +27,7 @@ export class MarsRover {
   private _directionIndex = 0;
   private _x: number = 0;
   private _y: number = 0;
+  private _gridSize = 10;
 
   execute(commands: string): string {
     for (const command of commands) {
@@ -63,7 +64,7 @@ export class MarsRover {
   private moveForward(): void {
     switch (this.currentDirection()) {
       case CompassDirection.North: {
-        this._y = this._y + 1;
+        this._y = (this._y + 1) % this._gridSize;
         break;
       }
       case CompassDirection.South: {

From 5ea807fdf2302a06f9c935e4e48ed3b3bc2dcf93 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:20:48 +0100
Subject: [PATCH 31/54] (RED) Add failing test south bound

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 345ab90..5c09d99 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -19,6 +19,7 @@ describe('mars rover should', () => {
     ['move forward facing east', 'RM', '1:0:E'],
     ['move forward facing west', 'RMLLM', '0:0:W'],
     ['wrap around north edge to bottom', 'MMMMMMMMMM', '0:0:N'],
+    ['wrap around south edge to top', 'RRMMMMMMMMMM', '0:0:S'],
   ])('%s', (_, input, expected) => {
     const actual = marsRover.execute(input);
 

From 5ab0bb145645ca70e818ca7ecddc600697f843ad Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:21:00 +0100
Subject: [PATCH 32/54] (GREEN) Fix failing  test

---
 test-pnpm/mars_rovers/mars.rover.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index dd56d6c..beb6f49 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -68,7 +68,7 @@ export class MarsRover {
         break;
       }
       case CompassDirection.South: {
-        this._y = this._y - 1;
+        this._y = (this._y - 1) % this._gridSize;
         break;
       }
       case CompassDirection.East: {

From 8cfe65712f990246cda69b0bb720883e917c11fb Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:23:01 +0100
Subject: [PATCH 33/54] (RED) Add failing test east bound

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 5c09d99..ac0f736 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -20,6 +20,7 @@ describe('mars rover should', () => {
     ['move forward facing west', 'RMLLM', '0:0:W'],
     ['wrap around north edge to bottom', 'MMMMMMMMMM', '0:0:N'],
     ['wrap around south edge to top', 'RRMMMMMMMMMM', '0:0:S'],
+    ['wrap around east edge left', 'RMMMMMMMMMM', '0:0:E'],
   ])('%s', (_, input, expected) => {
     const actual = marsRover.execute(input);
 

From 32e52dc040d352db76b64e13b568f5e523707b07 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:23:10 +0100
Subject: [PATCH 34/54] (GREEN) Fix failing test

---
 test-pnpm/mars_rovers/mars.rover.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index beb6f49..fe2fd3e 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -72,7 +72,7 @@ export class MarsRover {
         break;
       }
       case CompassDirection.East: {
-        this._x = this._x + 1;
+        this._x = (this._x + 1) % this._gridSize;
         break;
       }
       case CompassDirection.West: {

From 886465bb785721ace850276310e8025e1389bac0 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:25:42 +0100
Subject: [PATCH 35/54] (RED) Add failing test west  bound

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index ac0f736..ad8551e 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -20,7 +20,8 @@ describe('mars rover should', () => {
     ['move forward facing west', 'RMLLM', '0:0:W'],
     ['wrap around north edge to bottom', 'MMMMMMMMMM', '0:0:N'],
     ['wrap around south edge to top', 'RRMMMMMMMMMM', '0:0:S'],
-    ['wrap around east edge left', 'RMMMMMMMMMM', '0:0:E'],
+    ['wrap around east edge to the left', 'RMMMMMMMMMM', '0:0:E'],
+    ['wrap around west edge to the right', 'LMMMMMMMMMM', '0:0:W'],
   ])('%s', (_, input, expected) => {
     const actual = marsRover.execute(input);
 

From bd7b6cf6b8b2c994526e401b8e94e9688a631381 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:25:55 +0100
Subject: [PATCH 36/54] (GREEN) Fix failing test

---
 test-pnpm/mars_rovers/mars.rover.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index fe2fd3e..a41d844 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -76,7 +76,7 @@ export class MarsRover {
         break;
       }
       case CompassDirection.West: {
-        this._x = this._x - 1;
+        this._x = (this._x - 1) % this._gridSize;
         break;
       }
     }

From 698086eb86eddf76ac4f82e267aaf74647510cec Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 17:27:16 +0100
Subject: [PATCH 37/54] (REFACTOR): Group tests so it is easier to understand

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index ad8551e..c9c1e9b 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -9,15 +9,18 @@ describe('mars rover should', () => {
 
   test.each([
     ['report its default start position', '', '0:0:N'],
+
     ['move in the same direction with a single move command', 'M', '0:1:N'],
     ['move forward and then turn facing south', 'MRRM', '0:0:S'],
+    ['move in the same direction with a double move command', 'MM', '0:2:N'],
+    ['move forward facing east', 'RM', '1:0:E'],
+    ['move forward facing west', 'RMLLM', '0:0:W'],
+
     ['turn right facing east', 'R', '0:0:E'],
     ['turn right twice facing south', 'RR', '0:0:S'],
     ['turn right 4 times and face north again', 'RRRR', '0:0:N'],
     ['turn left facing west', 'L', '0:0:W'],
-    ['move in the same direction with a double move command', 'MM', '0:2:N'],
-    ['move forward facing east', 'RM', '1:0:E'],
-    ['move forward facing west', 'RMLLM', '0:0:W'],
+
     ['wrap around north edge to bottom', 'MMMMMMMMMM', '0:0:N'],
     ['wrap around south edge to top', 'RRMMMMMMMMMM', '0:0:S'],
     ['wrap around east edge to the left', 'RMMMMMMMMMM', '0:0:E'],

From d6493d2c556de4590bd1a55a42c41cdf38a3b8b8 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 18:06:35 +0100
Subject: [PATCH 38/54] (REFACTOR): Extract Position class to rid primitive
 obsession & tight coupling

---
 test-pnpm/mars_rovers/mars.rover.ts | 15 ++++++++-------
 test-pnpm/mars_rovers/position.ts   |  6 ++++++
 2 files changed, 14 insertions(+), 7 deletions(-)
 create mode 100644 test-pnpm/mars_rovers/position.ts

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index a41d844..c334e80 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -1,3 +1,5 @@
+import { Position } from './position';
+
 type Direction =
   | CompassDirection.North
   | CompassDirection.East
@@ -18,6 +20,7 @@ enum CommandType {
 }
 
 export class MarsRover {
+  private _position = new Position(0, 0);
   private _directions: Direction[] = new Array<Direction>(
     CompassDirection.North,
     CompassDirection.East,
@@ -25,8 +28,6 @@ export class MarsRover {
     CompassDirection.West,
   );
   private _directionIndex = 0;
-  private _x: number = 0;
-  private _y: number = 0;
   private _gridSize = 10;
 
   execute(commands: string): string {
@@ -44,7 +45,7 @@ export class MarsRover {
       }
     }
 
-    return `${this._x}:${this._y}:${this.currentDirection()}`;
+    return `${this._position.x}:${this._position.y}:${this.currentDirection()}`;
   }
 
   private currentDirection(): Direction {
@@ -64,19 +65,19 @@ export class MarsRover {
   private moveForward(): void {
     switch (this.currentDirection()) {
       case CompassDirection.North: {
-        this._y = (this._y + 1) % this._gridSize;
+        this._position.y = (this._position.y + 1) % this._gridSize;
         break;
       }
       case CompassDirection.South: {
-        this._y = (this._y - 1) % this._gridSize;
+        this._position.y = (this._position.y - 1) % this._gridSize;
         break;
       }
       case CompassDirection.East: {
-        this._x = (this._x + 1) % this._gridSize;
+        this._position.x = (this._position.x + 1) % this._gridSize;
         break;
       }
       case CompassDirection.West: {
-        this._x = (this._x - 1) % this._gridSize;
+        this._position.x = (this._position.x - 1) % this._gridSize;
         break;
       }
     }
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
new file mode 100644
index 0000000..38116d8
--- /dev/null
+++ b/test-pnpm/mars_rovers/position.ts
@@ -0,0 +1,6 @@
+export class Position {
+  constructor(
+    public x: number,
+    public y: number,
+  ) {}
+}

From 2908174d988833f335f92d44215d7b24b1b5a6c8 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 18:31:48 +0100
Subject: [PATCH 39/54] (REFACTOR): Move north positioning ontoPosition

---
 test-pnpm/mars_rovers/mars.rover.ts | 2 +-
 test-pnpm/mars_rovers/position.ts   | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index c334e80..ef55069 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -65,7 +65,7 @@ export class MarsRover {
   private moveForward(): void {
     switch (this.currentDirection()) {
       case CompassDirection.North: {
-        this._position.y = (this._position.y + 1) % this._gridSize;
+        this._position = this._position.moveNorth(this._gridSize);
         break;
       }
       case CompassDirection.South: {
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index 38116d8..09790f9 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -3,4 +3,8 @@ export class Position {
     public x: number,
     public y: number,
   ) {}
+
+  moveNorth(gridSize: number): Position {
+    return new Position(this.x, (this.y + 1) % gridSize);
+  }
 }

From 8d5f1ffb9d14b701314f11d86ecd18e872f2ccf0 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 18:35:10 +0100
Subject: [PATCH 40/54] (REFACTOR): Move south positioning onto Position

---
 test-pnpm/mars_rovers/mars.rover.ts | 2 +-
 test-pnpm/mars_rovers/position.ts   | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index ef55069..4b17e72 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -69,7 +69,7 @@ export class MarsRover {
         break;
       }
       case CompassDirection.South: {
-        this._position.y = (this._position.y - 1) % this._gridSize;
+        this._position = this._position.moveSouth(this._gridSize);
         break;
       }
       case CompassDirection.East: {
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index 09790f9..46dae4f 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -7,4 +7,8 @@ export class Position {
   moveNorth(gridSize: number): Position {
     return new Position(this.x, (this.y + 1) % gridSize);
   }
+
+  moveSouth(gridSize: number): Position {
+    return new Position(this.x, (this.y - 1) % gridSize);
+  }
 }

From a99ee73f9f976becf65cc9dee4e75f730334cc6f Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 18:38:17 +0100
Subject: [PATCH 41/54] (REFACTOR): Move east  positioning onto Position

---
 test-pnpm/mars_rovers/mars.rover.ts | 2 +-
 test-pnpm/mars_rovers/position.ts   | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 4b17e72..3dd1d83 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -73,7 +73,7 @@ export class MarsRover {
         break;
       }
       case CompassDirection.East: {
-        this._position.x = (this._position.x + 1) % this._gridSize;
+        this._position = this._position.moveEast(this._gridSize);
         break;
       }
       case CompassDirection.West: {
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index 46dae4f..f51f9f7 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -11,4 +11,8 @@ export class Position {
   moveSouth(gridSize: number): Position {
     return new Position(this.x, (this.y - 1) % gridSize);
   }
+
+  moveEast(gridSize: number): Position {
+    return new Position((this.x + 1) % gridSize, this.y);
+  }
 }

From 7fe3ca5276ead81863a0c8265de781d3ba359021 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 18:44:01 +0100
Subject: [PATCH 42/54] (REFACTOR): Move west and seal position

---
 test-pnpm/mars_rovers/mars.rover.ts | 2 +-
 test-pnpm/mars_rovers/position.ts   | 8 ++++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 3dd1d83..bc7dc2e 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -77,7 +77,7 @@ export class MarsRover {
         break;
       }
       case CompassDirection.West: {
-        this._position.x = (this._position.x - 1) % this._gridSize;
+        this._position = this._position.moveWest(this._gridSize);
         break;
       }
     }
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index f51f9f7..820bbd8 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -1,7 +1,7 @@
 export class Position {
   constructor(
-    public x: number,
-    public y: number,
+    public readonly x: number,
+    public readonly y: number,
   ) {}
 
   moveNorth(gridSize: number): Position {
@@ -15,4 +15,8 @@ export class Position {
   moveEast(gridSize: number): Position {
     return new Position((this.x + 1) % gridSize, this.y);
   }
+
+  moveWest(gridSize: number): Position {
+    return new Position((this.x - 1) % gridSize, this.y);
+  }
 }

From 708ab9a54f47a0ddcf1bf5ad19526644e75982a2 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 18:50:01 +0100
Subject: [PATCH 43/54] (REFACTOR): Move position corodinates  as string

---
 test-pnpm/mars_rovers/mars.rover.ts | 2 +-
 test-pnpm/mars_rovers/position.ts   | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index bc7dc2e..48c6049 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -45,7 +45,7 @@ export class MarsRover {
       }
     }
 
-    return `${this._position.x}:${this._position.y}:${this.currentDirection()}`;
+    return `${this._position.toString()}:${this.currentDirection()}`;
   }
 
   private currentDirection(): Direction {
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index 820bbd8..99be5a3 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -19,4 +19,8 @@ export class Position {
   moveWest(gridSize: number): Position {
     return new Position((this.x - 1) % gridSize, this.y);
   }
+
+  toString(): string {
+    return `${this.x}:${this.y}`;
+  }
 }

From 2547e0f240f1ecd0881af6198da5b8f29a3031c8 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 18:51:43 +0100
Subject: [PATCH 44/54] (REFACTOR): Reduce switch to tuple

---
 test-pnpm/mars_rovers/mars.rover.ts | 25 +++++++------------------
 1 file changed, 7 insertions(+), 18 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 48c6049..928b01e 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -63,23 +63,12 @@ export class MarsRover {
   }
 
   private moveForward(): void {
-    switch (this.currentDirection()) {
-      case CompassDirection.North: {
-        this._position = this._position.moveNorth(this._gridSize);
-        break;
-      }
-      case CompassDirection.South: {
-        this._position = this._position.moveSouth(this._gridSize);
-        break;
-      }
-      case CompassDirection.East: {
-        this._position = this._position.moveEast(this._gridSize);
-        break;
-      }
-      case CompassDirection.West: {
-        this._position = this._position.moveWest(this._gridSize);
-        break;
-      }
-    }
+    const positionMap: Record<CompassDirection, () => Position> = {
+      [CompassDirection.North]: () => this._position.moveNorth(this._gridSize),
+      [CompassDirection.South]: () => this._position.moveSouth(this._gridSize),
+      [CompassDirection.East]: () => this._position.moveEast(this._gridSize),
+      [CompassDirection.West]: () => this._position.moveWest(this._gridSize),
+    };
+    this._position = positionMap[this.currentDirection()]();
   }
 }

From b5f55aee0b6f0fa9ac71e3dfb5d71c43d049c3d6 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 19:49:35 +0100
Subject: [PATCH 45/54] (REFACTOR): Extract Direction and refactor rover

---
 test-pnpm/mars_rovers/direction.ts  | 31 ++++++++++++++++++++++++++++
 test-pnpm/mars_rovers/mars.rover.ts | 32 ++++++-----------------------
 2 files changed, 37 insertions(+), 26 deletions(-)
 create mode 100644 test-pnpm/mars_rovers/direction.ts

diff --git a/test-pnpm/mars_rovers/direction.ts b/test-pnpm/mars_rovers/direction.ts
new file mode 100644
index 0000000..5b0bd27
--- /dev/null
+++ b/test-pnpm/mars_rovers/direction.ts
@@ -0,0 +1,31 @@
+export enum CompassDirection {
+  North = 'N',
+  East = 'E',
+  South = 'S',
+  West = 'W',
+}
+
+export class Direction {
+  private _directions: CompassDirection[];
+
+  constructor(public readonly value: CompassDirection) {
+    this._directions = new Array<CompassDirection>(
+      CompassDirection.North,
+      CompassDirection.East,
+      CompassDirection.South,
+      CompassDirection.West,
+    );
+  }
+
+  rotateLeft(): Direction {
+    const index = this._directions.indexOf(this.value);
+    const newIndex = (index - 1 + this._directions.length) % this._directions.length;
+    return new Direction(this._directions[newIndex]);
+  }
+
+  rotateRight(): Direction {
+    const index = this._directions.indexOf(this.value);
+    const newIndex = (index + 1 + this._directions.length) % this._directions.length;
+    return new Direction(this._directions[newIndex]);
+  }
+}
diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 928b01e..d9c8e9e 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -1,18 +1,6 @@
+import { CompassDirection, Direction } from './direction';
 import { Position } from './position';
 
-type Direction =
-  | CompassDirection.North
-  | CompassDirection.East
-  | CompassDirection.South
-  | CompassDirection.West;
-
-enum CompassDirection {
-  North = 'N',
-  East = 'E',
-  South = 'S',
-  West = 'W',
-}
-
 enum CommandType {
   Move = 'M',
   TurnRight = 'R',
@@ -21,13 +9,7 @@ enum CommandType {
 
 export class MarsRover {
   private _position = new Position(0, 0);
-  private _directions: Direction[] = new Array<Direction>(
-    CompassDirection.North,
-    CompassDirection.East,
-    CompassDirection.South,
-    CompassDirection.West,
-  );
-  private _directionIndex = 0;
+  private _direction = new Direction(CompassDirection.North);
   private _gridSize = 10;
 
   execute(commands: string): string {
@@ -48,18 +30,16 @@ export class MarsRover {
     return `${this._position.toString()}:${this.currentDirection()}`;
   }
 
-  private currentDirection(): Direction {
-    return this._directions[this._directionIndex];
+  private currentDirection(): CompassDirection {
+    return this._direction.value;
   }
 
   private moveLeft(): void {
-    // subtract 1 but wrap around if < 0
-    this._directionIndex =
-      (this._directionIndex - 1 + this._directions.length) % this._directions.length;
+    this._direction = this._direction.rotateLeft();
   }
 
   private moveRight(): void {
-    this._directionIndex = (this._directionIndex + 1) % this._directions.length;
+    this._direction = this._direction.rotateRight();
   }
 
   private moveForward(): void {

From 425dec038276711287cf9d0ef285ca00e9bed1c0 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 20:16:32 +0100
Subject: [PATCH 46/54] (REFACTOR): Fix law of demeter violation

---
 test-pnpm/mars_rovers/mars.rover.ts | 25 +++++++------------------
 test-pnpm/mars_rovers/position.ts   | 23 +++++++++++++++++++----
 2 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index d9c8e9e..9ba7a5e 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -11,20 +11,15 @@ export class MarsRover {
   private _position = new Position(0, 0);
   private _direction = new Direction(CompassDirection.North);
   private _gridSize = 10;
+  private readonly commandHandlers: Record<CommandType, () => void> = {
+    [CommandType.Move]: () => this.moveForward(),
+    [CommandType.TurnRight]: () => this.moveRight(),
+    [CommandType.TurnLeft]: () => this.moveLeft(),
+  };
 
   execute(commands: string): string {
     for (const command of commands) {
-      switch (command) {
-        case CommandType.Move:
-          this.moveForward();
-          break;
-        case CommandType.TurnRight:
-          this.moveRight();
-          break;
-        case CommandType.TurnLeft:
-          this.moveLeft();
-          break;
-      }
+      this.commandHandlers[command]();
     }
 
     return `${this._position.toString()}:${this.currentDirection()}`;
@@ -43,12 +38,6 @@ export class MarsRover {
   }
 
   private moveForward(): void {
-    const positionMap: Record<CompassDirection, () => Position> = {
-      [CompassDirection.North]: () => this._position.moveNorth(this._gridSize),
-      [CompassDirection.South]: () => this._position.moveSouth(this._gridSize),
-      [CompassDirection.East]: () => this._position.moveEast(this._gridSize),
-      [CompassDirection.West]: () => this._position.moveWest(this._gridSize),
-    };
-    this._position = positionMap[this.currentDirection()]();
+    this._position = this._position.move(this.currentDirection(), this._gridSize);
   }
 }
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index 99be5a3..54fb578 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -1,22 +1,37 @@
+import { CompassDirection } from './direction';
+
 export class Position {
   constructor(
     public readonly x: number,
     public readonly y: number,
   ) {}
 
-  moveNorth(gridSize: number): Position {
+  move(direction: CompassDirection, gridSize: number): Position {
+    switch (direction) {
+      case CompassDirection.North:
+        return this.moveNorth(gridSize);
+      case CompassDirection.South:
+        return this.moveSouth(gridSize);
+      case CompassDirection.East:
+        return this.moveEast(gridSize);
+      case CompassDirection.West:
+        return this.moveWest(gridSize);
+    }
+  }
+
+  private moveNorth(gridSize: number): Position {
     return new Position(this.x, (this.y + 1) % gridSize);
   }
 
-  moveSouth(gridSize: number): Position {
+  private moveSouth(gridSize: number): Position {
     return new Position(this.x, (this.y - 1) % gridSize);
   }
 
-  moveEast(gridSize: number): Position {
+  private moveEast(gridSize: number): Position {
     return new Position((this.x + 1) % gridSize, this.y);
   }
 
-  moveWest(gridSize: number): Position {
+  private moveWest(gridSize: number): Position {
     return new Position((this.x - 1) % gridSize, this.y);
   }
 

From e7e5ad83066cdc75bea4900b913c32e4edee98f9 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sat, 17 May 2025 20:25:03 +0100
Subject: [PATCH 47/54] (REFACTOR): Add and refactor final full tests with no
 obstacles

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index c9c1e9b..8cb66a8 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -25,7 +25,10 @@ describe('mars rover should', () => {
     ['wrap around south edge to top', 'RRMMMMMMMMMM', '0:0:S'],
     ['wrap around east edge to the left', 'RMMMMMMMMMM', '0:0:E'],
     ['wrap around west edge to the right', 'LMMMMMMMMMM', '0:0:W'],
-  ])('%s', (_, input, expected) => {
+
+    ['given a grid with no obstacles', 'MMRMMLM', '2:3:N'],
+    ['given a grid with no obstacles', 'MMMMMMMMMM', '0:0:N'],
+  ])('%s with input %s outputs %s', (_, input, expected) => {
     const actual = marsRover.execute(input);
 
     expect(actual).toBe(expected);

From ddec397915d4732438900e59e803df456e2c21ff Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sun, 18 May 2025 12:23:32 +0100
Subject: [PATCH 48/54] (REFACTOR): Fix case to get back into it

---
 test-pnpm/mars_rovers/position.ts | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index 54fb578..fb845a9 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -7,16 +7,12 @@ export class Position {
   ) {}
 
   move(direction: CompassDirection, gridSize: number): Position {
-    switch (direction) {
-      case CompassDirection.North:
-        return this.moveNorth(gridSize);
-      case CompassDirection.South:
-        return this.moveSouth(gridSize);
-      case CompassDirection.East:
-        return this.moveEast(gridSize);
-      case CompassDirection.West:
-        return this.moveWest(gridSize);
-    }
+    return {
+      [CompassDirection.North]: () => this.moveNorth(gridSize),
+      [CompassDirection.East]: () => this.moveEast(gridSize),
+      [CompassDirection.South]: () => this.moveSouth(gridSize),
+      [CompassDirection.West]: () => this.moveWest(gridSize),
+    }[direction]();
   }
 
   private moveNorth(gridSize: number): Position {

From 4dbb0e811cf6bb22190cb7e47416f6561486656b Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sun, 18 May 2025 14:30:22 +0100
Subject: [PATCH 49/54] (RED) Add failing test for obstacle

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 8cb66a8..8109478 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -1,4 +1,5 @@
 import { MarsRover } from './mars.rover';
+import { Position } from './position';
 
 describe('mars rover should', () => {
   let marsRover: MarsRover;
@@ -33,4 +34,15 @@ describe('mars rover should', () => {
 
     expect(actual).toBe(expected);
   });
+
+  describe('when given obstacles should', () => {
+    test('navigate up to the obstacle and no further', () => {
+      var obstacle = new Position(0, 3);
+      marsRover = new MarsRover([obstacle]);
+
+      var actual = marsRover.execute('MMMM');
+
+      expect(actual).toBe('O:0:2:N');
+    });
+  });
 });

From 23f9714e50f3fa89cf36936ef99dbce7408d0345 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sun, 18 May 2025 14:40:57 +0100
Subject: [PATCH 50/54] (GREEN) Fix failing obstacle test

---
 test-pnpm/mars_rovers/mars.rover.ts | 31 +++++++++++++++++++----------
 test-pnpm/mars_rovers/position.ts   | 20 +++++++++++++------
 2 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 9ba7a5e..efb3f16 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -8,21 +8,29 @@ enum CommandType {
 }
 
 export class MarsRover {
-  private _position = new Position(0, 0);
-  private _direction = new Direction(CompassDirection.North);
-  private _gridSize = 10;
-  private readonly commandHandlers: Record<CommandType, () => void> = {
-    [CommandType.Move]: () => this.moveForward(),
-    [CommandType.TurnRight]: () => this.moveRight(),
-    [CommandType.TurnLeft]: () => this.moveLeft(),
-  };
+  private _position: Position;
+  private _direction: Direction;
+  private readonly commandHandlers: Record<CommandType, () => void>;
+
+  constructor(
+    obstacles: Array<Position> | null = null,
+    private readonly _gridSize = 10,
+  ) {
+    this._position = new Position(0, 0, obstacles);
+    this._direction = new Direction(CompassDirection.North);
+    this.commandHandlers = {
+      [CommandType.Move]: () => this.moveForward(),
+      [CommandType.TurnRight]: () => this.moveRight(),
+      [CommandType.TurnLeft]: () => this.moveLeft(),
+    };
+  }
 
   execute(commands: string): string {
     for (const command of commands) {
       this.commandHandlers[command]();
     }
 
-    return `${this._position.toString()}:${this.currentDirection()}`;
+    return `${this._position.toString(this.currentDirection(), this._gridSize)}`;
   }
 
   private currentDirection(): CompassDirection {
@@ -38,6 +46,9 @@ export class MarsRover {
   }
 
   private moveForward(): void {
-    this._position = this._position.move(this.currentDirection(), this._gridSize);
+    const nextPosition = this._position.move(this.currentDirection(), this._gridSize);
+    if (!nextPosition.hasObstacle()) {
+      this._position = nextPosition;
+    }
   }
 }
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index fb845a9..a493039 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -4,6 +4,7 @@ export class Position {
   constructor(
     public readonly x: number,
     public readonly y: number,
+    public readonly obstacles: Array<Position> = null,
   ) {}
 
   move(direction: CompassDirection, gridSize: number): Position {
@@ -15,23 +16,30 @@ export class Position {
     }[direction]();
   }
 
+  hasObstacle(): boolean {
+    return this.obstacles?.some((obstacle) => obstacle.x === this.x && obstacle.y === this.y);
+  }
+
   private moveNorth(gridSize: number): Position {
-    return new Position(this.x, (this.y + 1) % gridSize);
+    return new Position(this.x, (this.y + 1) % gridSize, this.obstacles);
   }
 
   private moveSouth(gridSize: number): Position {
-    return new Position(this.x, (this.y - 1) % gridSize);
+    return new Position(this.x, (this.y - 1) % gridSize, this.obstacles);
   }
 
   private moveEast(gridSize: number): Position {
-    return new Position((this.x + 1) % gridSize, this.y);
+    return new Position((this.x + 1) % gridSize, this.y, this.obstacles);
   }
 
   private moveWest(gridSize: number): Position {
-    return new Position((this.x - 1) % gridSize, this.y);
+    return new Position((this.x - 1 + gridSize) % gridSize, this.y, this.obstacles);
   }
 
-  toString(): string {
-    return `${this.x}:${this.y}`;
+  toString(currentDirection: CompassDirection, gridSize: number): string {
+    const nextMove = this.move(currentDirection, gridSize);
+    const OBSTACLE_PREFIX = 'O:';
+    const NO_PREFIX = '';
+    return `${nextMove.hasObstacle() ? OBSTACLE_PREFIX : NO_PREFIX}${this.x}:${this.y}:${currentDirection}`;
   }
 }

From 3431ad61b01f0daf06cf51b6792cf4645754015d Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sun, 18 May 2025 15:30:06 +0100
Subject: [PATCH 51/54] (RED) Refactor to extract grid

---
 test-pnpm/mars_rovers/mars.rover.should.test.ts | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 8109478..060086c 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -1,11 +1,14 @@
+import { Grid } from './grid';
 import { MarsRover } from './mars.rover';
 import { Position } from './position';
 
 describe('mars rover should', () => {
+  let grid: Grid;
   let marsRover: MarsRover;
 
   beforeEach(() => {
-    marsRover = new MarsRover();
+    grid = new Grid();
+    marsRover = new MarsRover(grid);
   });
 
   test.each([
@@ -38,7 +41,8 @@ describe('mars rover should', () => {
   describe('when given obstacles should', () => {
     test('navigate up to the obstacle and no further', () => {
       var obstacle = new Position(0, 3);
-      marsRover = new MarsRover([obstacle]);
+      grid = new Grid([obstacle]);
+      marsRover = new MarsRover(grid);
 
       var actual = marsRover.execute('MMMM');
 

From 1d8b39ae9b628eb26fc8a273778c6ae408eaf48b Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sun, 18 May 2025 15:31:53 +0100
Subject: [PATCH 52/54] (GREEN/REFACTOR) Centralise grid logic Decouple
 position from obstacle presence Improve Wrap logic on the grid to be more
 redable

---
 test-pnpm/mars_rovers/grid.ts       | 24 +++++++++++++++++
 test-pnpm/mars_rovers/mars.rover.ts | 19 +++++++------
 test-pnpm/mars_rovers/position.ts   | 42 +++++++----------------------
 3 files changed, 43 insertions(+), 42 deletions(-)
 create mode 100644 test-pnpm/mars_rovers/grid.ts

diff --git a/test-pnpm/mars_rovers/grid.ts b/test-pnpm/mars_rovers/grid.ts
new file mode 100644
index 0000000..383e63d
--- /dev/null
+++ b/test-pnpm/mars_rovers/grid.ts
@@ -0,0 +1,24 @@
+import { Position } from './position';
+
+export type Cordinate = {
+  x: number;
+  y: number;
+};
+
+export class Grid {
+  constructor(
+    private readonly _obstacles: Array<Position> | null = null,
+    public readonly size: number = 10,
+  ) {}
+
+  hasObstacle(x: number, y: number): boolean {
+    return this._obstacles?.some((obstacle) => obstacle.x === x && obstacle.y === y);
+  }
+
+  wrap(x: number, y: number): Cordinate {
+    return {
+      x: (x + this.size) % this.size,
+      y: (y + this.size) % this.size,
+    };
+  }
+}
diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index efb3f16..77087b9 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -1,4 +1,5 @@
 import { CompassDirection, Direction } from './direction';
+import { Grid } from './grid';
 import { Position } from './position';
 
 enum CommandType {
@@ -12,11 +13,8 @@ export class MarsRover {
   private _direction: Direction;
   private readonly commandHandlers: Record<CommandType, () => void>;
 
-  constructor(
-    obstacles: Array<Position> | null = null,
-    private readonly _gridSize = 10,
-  ) {
-    this._position = new Position(0, 0, obstacles);
+  constructor(private readonly _grid: Grid) {
+    this._position = new Position(0, 0);
     this._direction = new Direction(CompassDirection.North);
     this.commandHandlers = {
       [CommandType.Move]: () => this.moveForward(),
@@ -29,8 +27,9 @@ export class MarsRover {
     for (const command of commands) {
       this.commandHandlers[command]();
     }
-
-    return `${this._position.toString(this.currentDirection(), this._gridSize)}`;
+C    const next = this._position.move(this.currentDirection(), this._grid);
+    const prefix = this._grid.hasObstacle(next.x, next.y) ? 'O:' : '';
+    return `${prefix}${this._position.toString()}:${this._direction.value}`;
   }
 
   private currentDirection(): CompassDirection {
@@ -46,9 +45,9 @@ export class MarsRover {
   }
 
   private moveForward(): void {
-    const nextPosition = this._position.move(this.currentDirection(), this._gridSize);
-    if (!nextPosition.hasObstacle()) {
-      this._position = nextPosition;
+    const next = this._position.move(this.currentDirection(), this._grid);
+    if (!this._grid.hasObstacle(next.x, next.y)) {
+      this._position = next;
     }
   }
 }
diff --git a/test-pnpm/mars_rovers/position.ts b/test-pnpm/mars_rovers/position.ts
index a493039..b3f1566 100644
--- a/test-pnpm/mars_rovers/position.ts
+++ b/test-pnpm/mars_rovers/position.ts
@@ -1,45 +1,23 @@
 import { CompassDirection } from './direction';
+import { Grid } from './grid';
 
 export class Position {
   constructor(
     public readonly x: number,
     public readonly y: number,
-    public readonly obstacles: Array<Position> = null,
   ) {}
 
-  move(direction: CompassDirection, gridSize: number): Position {
-    return {
-      [CompassDirection.North]: () => this.moveNorth(gridSize),
-      [CompassDirection.East]: () => this.moveEast(gridSize),
-      [CompassDirection.South]: () => this.moveSouth(gridSize),
-      [CompassDirection.West]: () => this.moveWest(gridSize),
+  move(direction: CompassDirection, grid: Grid): Position {
+    const { x, y } = {
+      [CompassDirection.North]: () => grid.wrap(this.x, this.y + 1),
+      [CompassDirection.South]: () => grid.wrap(this.x, this.y - 1),
+      [CompassDirection.East]: () => grid.wrap(this.x + 1, this.y),
+      [CompassDirection.West]: () => grid.wrap(this.x - 1, this.y),
     }[direction]();
+    return new Position(x, y);
   }
 
-  hasObstacle(): boolean {
-    return this.obstacles?.some((obstacle) => obstacle.x === this.x && obstacle.y === this.y);
-  }
-
-  private moveNorth(gridSize: number): Position {
-    return new Position(this.x, (this.y + 1) % gridSize, this.obstacles);
-  }
-
-  private moveSouth(gridSize: number): Position {
-    return new Position(this.x, (this.y - 1) % gridSize, this.obstacles);
-  }
-
-  private moveEast(gridSize: number): Position {
-    return new Position((this.x + 1) % gridSize, this.y, this.obstacles);
-  }
-
-  private moveWest(gridSize: number): Position {
-    return new Position((this.x - 1 + gridSize) % gridSize, this.y, this.obstacles);
-  }
-
-  toString(currentDirection: CompassDirection, gridSize: number): string {
-    const nextMove = this.move(currentDirection, gridSize);
-    const OBSTACLE_PREFIX = 'O:';
-    const NO_PREFIX = '';
-    return `${nextMove.hasObstacle() ? OBSTACLE_PREFIX : NO_PREFIX}${this.x}:${this.y}:${currentDirection}`;
+  toString(): string {
+    return `${this.x}:${this.y}`;
   }
 }

From 14832e1a31372b86402fc7d744bf51a2c9d6daa6 Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sun, 18 May 2025 15:45:51 +0100
Subject: [PATCH 53/54] (REFACTOR) Clean up test with GridBuilder

---
 test-pnpm/mars_rovers/grid.builder.ts         | 21 +++++++++++++++++++
 .../mars_rovers/mars.rover.should.test.ts     |  6 +++---
 test-pnpm/mars_rovers/mars.rover.ts           |  2 +-
 3 files changed, 25 insertions(+), 4 deletions(-)
 create mode 100644 test-pnpm/mars_rovers/grid.builder.ts

diff --git a/test-pnpm/mars_rovers/grid.builder.ts b/test-pnpm/mars_rovers/grid.builder.ts
new file mode 100644
index 0000000..f2e5bd9
--- /dev/null
+++ b/test-pnpm/mars_rovers/grid.builder.ts
@@ -0,0 +1,21 @@
+import { Grid } from './grid';
+import { Position } from './position';
+
+export class GridBuilder {
+  private _size: number = 10;
+  private _obstacles: Array<Position>;
+
+  withSize(size: number): this {
+    this._size = size;
+    return this;
+  }
+
+  withObstacles(...obstacles: Position[]): this {
+    this._obstacles = obstacles;
+    return this;
+  }
+
+  buid(): Grid {
+    return new Grid(this._obstacles, this._size);
+  }
+}
diff --git a/test-pnpm/mars_rovers/mars.rover.should.test.ts b/test-pnpm/mars_rovers/mars.rover.should.test.ts
index 060086c..c2b72c8 100644
--- a/test-pnpm/mars_rovers/mars.rover.should.test.ts
+++ b/test-pnpm/mars_rovers/mars.rover.should.test.ts
@@ -1,4 +1,5 @@
 import { Grid } from './grid';
+import { GridBuilder } from './grid.builder';
 import { MarsRover } from './mars.rover';
 import { Position } from './position';
 
@@ -7,7 +8,7 @@ describe('mars rover should', () => {
   let marsRover: MarsRover;
 
   beforeEach(() => {
-    grid = new Grid();
+    grid = new GridBuilder().withSize(10).buid();
     marsRover = new MarsRover(grid);
   });
 
@@ -40,8 +41,7 @@ describe('mars rover should', () => {
 
   describe('when given obstacles should', () => {
     test('navigate up to the obstacle and no further', () => {
-      var obstacle = new Position(0, 3);
-      grid = new Grid([obstacle]);
+      grid = new GridBuilder().withSize(10).withObstacles(new Position(0, 3)).buid();
       marsRover = new MarsRover(grid);
 
       var actual = marsRover.execute('MMMM');
diff --git a/test-pnpm/mars_rovers/mars.rover.ts b/test-pnpm/mars_rovers/mars.rover.ts
index 77087b9..c1aa90d 100644
--- a/test-pnpm/mars_rovers/mars.rover.ts
+++ b/test-pnpm/mars_rovers/mars.rover.ts
@@ -27,7 +27,7 @@ export class MarsRover {
     for (const command of commands) {
       this.commandHandlers[command]();
     }
-C    const next = this._position.move(this.currentDirection(), this._grid);
+    const next = this._position.move(this.currentDirection(), this._grid);
     const prefix = this._grid.hasObstacle(next.x, next.y) ? 'O:' : '';
     return `${prefix}${this._position.toString()}:${this._direction.value}`;
   }

From 89a356f6beafa6982e966f50bdbca28677ca93af Mon Sep 17 00:00:00 2001
From: Vincent Farah <vincent.farah@gbgplc.com>
Date: Sun, 18 May 2025 16:59:40 +0100
Subject: [PATCH 54/54] Its a wrap

---
 test-pnpm/mars_rovers/README.md | 38 +++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/test-pnpm/mars_rovers/README.md b/test-pnpm/mars_rovers/README.md
index 01383d5..4c88275 100644
--- a/test-pnpm/mars_rovers/README.md
+++ b/test-pnpm/mars_rovers/README.md
@@ -156,4 +156,42 @@ Add scenario-based tests:
 - Extract reusable logic (e.g. `rotate`, `nextPosition`)
 - Add immutability if you favour a purer style
 - Optionally expose state inspection for diagnostics/logging
+- Create a functional approach to the same Kata
 
+### Summary
+
+Thanks *Danil Suits* for your lovely kata. I put a lot of empasis on dicipline with RED, GREEN, REFACTOR pattern of TDD * INFINITY. I also tried harder than usual to identify the natural anti-patterns I was creating by keeping things small and simple, adding a reference to [refactoring smells](https://refactoring.guru/refactoring/smells) so you can see the anti patterns I added and tried to fix. Keep timing tight, which I didn't inbetween doing stuff and other unrelated activities. https://cuckoo.team/ is a great tool for that. If you are going to pair with someone, make sure you discuss some [principles and etiquette](https://www.thoughtworks.com/insights/blog/seven-principles-pair-programming-etiquette) around  what you need to do. Two controversial  points with my solution. One is *Typescript* and the other is *functional* vs *class*. I personally use both when appropriate and am not a real javascript purest or functional purest. Functional approaches shine when the state transitions are stateless and I want to you want to compose behaviour easily. Class-based approach shines when encapsulation of state and behaviour and *Object-Orientation* Models the domain well. I also find as I am in C# these days, it  just feels more natural to use and swap between it. 
+
+Verdict
+
+> **Your class-based approach is very clean and modular — not worse than functional, just different. You're modelling the domain responsibly.**
+
+A little bit of a break down into how you can prevent boiling the ocean :)
+
+The hard part was breaking it up to not do too much at a time, so lots of small tests driving small changes and requirments to introduce stuff.
+
+`''` → `0:0:N` ✅
+
+`'M'` → `0:1:N` ✅
+
+`'MM'` → `0:2:N` ✅
+
+`'R'` → `0:0:E` ✅
+
+Directional requirments seemed easier to expand by
+
+| Input  | Expected Output | Notes                                |
+| ------ | --------------- | ------------------------------------ |
+| `R`    | `0:0:E`         | North → East                         |
+| `RR`   | `0:0:S`         | East → South                         |
+| `RRR`  | `0:0:W`         | South → West                         |
+| `RRRR` | `0:0:N`         | Wrap-around to North (full rotation) |
+
+const directions = ['N', 'E', 'S', 'W']; // indices: 0, 1, 2, 3
+
+| Current index | +1   | Mod 4 (`% 4`) | New Direction |
+| ------------- | ---- | ------------- | ------------- |
+| 0 (N)         | 1    | 1             | E             |
+| 1 (E)         | 2    | 2             | S             |
+| 2 (S)         | 3    | 3             | W             |
+| 3 (W)         | 4    | 0             | N (wrap)      |
\ No newline at end of file