diff --git a/source/Trek-12/Tests/RulesTests.cs b/source/Trek-12/Tests/RulesTests.cs
new file mode 100644
index 0000000..56ec387
--- /dev/null
+++ b/source/Trek-12/Tests/RulesTests.cs
@@ -0,0 +1,235 @@
+namespace Tests;
+using Models.Game;
+using Models.Rules;
+
+public class RulesTests
+{
+    [Fact]
+    public void IsCellEmpty_ReturnsTrue_WhenCellIsNull()
+    {
+        Rules rules = new Rules();
+        Assert.True(rules.IsCellEmpty(null));
+    }
+    
+    [Fact]
+    public void IsCellEmpty_ReturnsTrue_WhenCellValueIsNull()
+    {
+        Rules rules = new Rules();
+        Cell cell = new Cell(0, 0);
+        Assert.True(rules.IsCellEmpty(cell));
+    }
+    
+    [Fact]
+    public void IsCellEmpty_ReturnsFalse_WhenCellValueIsNotNull()
+    {
+        Rules rules = new Rules();
+        Cell cell = new Cell(0, 0);
+        cell.Value = 1;
+        Assert.False(rules.IsCellEmpty(cell));
+    }
+    
+    [Fact]
+    public void IsCellValid_ReturnsFalse_WhenCellIsNotEmptyAndHasAdjacentCells()
+    {
+        Rules rules = new Rules();
+        Map map = new Map("background");
+        Cell selectedCell = map.Boards[0];
+        selectedCell.Value = 5;
+        Assert.False(rules.IsCellValid(selectedCell, map.Boards));
+    }
+    
+    [Fact]
+    public void IsCellValid_ReturnsTrue_WhenCellIsEmptyAndHasAdjacentCells()
+    {
+        Rules rules = new Rules();
+        Map map = new Map("background");
+        Cell selectedCell = map.Boards[0];
+        Assert.True(rules.IsCellValid(selectedCell, map.Boards));
+    }
+    
+    [Fact]
+    public void IsCellAdjacent_ReturnsFalse_WhenCellsAreNotAdjacent()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(2, 2);
+        Assert.False(rules.IsCellAdjacent(cell1, cell2));
+    }
+    
+    [Fact]
+    public void IsCellAdjacent_ReturnsTrue_WhenCellsAreSideBySide()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(0, 1);
+        Assert.True(rules.IsCellAdjacent(cell1, cell2));
+    }
+    
+    [Fact]
+    public void IsCellAdjacent_ReturnsTrue_WhenCellsAreDiagonal()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(1, 1);
+        Assert.True(rules.IsCellAdjacent(cell1, cell2));
+    }
+    
+    [Fact]
+    public void IsInRopePaths_ReturnsTrue_WhenCellsAreInRopePaths()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(0, 1);
+        Map map = new Map("background");
+        map.RopePaths.Add(new List<Cell> { cell1, cell2 });
+        Assert.True(rules.IsInRopePaths(cell2, map.RopePaths, 0));
+    }
+    
+    [Fact]
+    public void IsInRopePaths_ReturnsFalse_WhenCellsAreNotInRopePaths()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(0, 1);
+        Map map = new Map("background");
+        map.RopePaths.Add(new List<Cell> { cell1 });
+        Assert.False(rules.IsInRopePaths(cell2, map.RopePaths, 0));
+    }
+    
+    [Fact]
+    public void IsInRopePaths_ReturnsTrue_WhenCellsAreInRopePathsButNotInTheSamePath()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(0, 1);
+        Map map = new Map("background");
+        map.RopePaths.Add(new List<Cell> { cell1 });
+        map.RopePaths.Add(new List<Cell> { cell2 });
+        Assert.True(rules.IsInRopePaths(cell2, map.RopePaths, 0));
+    }
+    
+    [Fact]
+    public void AsValue_ReturnsTrue_WhenCellHasTheSameValue()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(0, 1);
+        cell1.Value = 5;
+        cell2.Value = 5;
+        Map map = new Map("background");
+        map.RopePaths.Add(new List<Cell> { cell1, cell2 });
+        Assert.True(rules.AsValue(cell2, map.RopePaths, 0));
+    }
+    
+    [Fact]
+    public void AsValue_ReturnsTrue_WhenCellValueIsAlreadyInRopePaths()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(0, 1);
+        cell1.Value = 5;
+        cell2.Value = 5;
+        Map map = new Map("background");
+        map.RopePaths.Add(new List<Cell> { cell1 });
+        Assert.True(rules.AsValue(cell2, map.RopePaths, 0));
+    }
+    
+    [Fact]
+    public void AsValue_ReturnsFalse_WhenCellHasDifferentValue()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(0, 1);
+        cell1.Value = 5;
+        cell2.Value = 6;
+        Map map = new Map("background");
+        map.RopePaths.Add(new List<Cell> { cell1 });
+        Assert.False(rules.AsValue(cell2, map.RopePaths, 0));
+    }
+    
+    [Fact]
+    public void NearCellIsValid_ReturnsFalse_WhenChosenCellIsNull()
+    {
+        Rules rules = new Rules();
+        Assert.False(rules.NearCellIsValid(null, new List<Cell>()));
+    }
+
+    [Fact]
+    public void NearCellIsValid_ReturnsFalse_WhenCellsIsNull()
+    {
+        Rules rules = new Rules();
+        Cell cell = new Cell(0, 0);
+        Assert.False(rules.NearCellIsValid(cell, null));
+    }
+
+    [Fact]
+    public void NearCellIsValid_ReturnsFalse_WhenNoAdjacentCells()
+    {
+        Rules rules = new Rules();
+        Cell cell = new Cell(0, 0);
+        List<Cell> cells = new List<Cell> { new Cell(2, 0) };
+        Assert.False(rules.NearCellIsValid(cell, cells));
+    }
+
+    [Fact]
+    public void NearCellIsValid_ReturnsTrue_WhenAdjacentCellExists()
+    {
+        Rules rules = new Rules();
+        Cell cell1 = new Cell(0, 0);
+        Cell cell2 = new Cell(0, 1);
+        cell2.Value = 12;
+        List<Cell> cells = new List<Cell> { cell2 };
+        Assert.True(rules.NearCellIsValid(cell1, cells));
+    }
+    
+    [Fact]
+    public void IsZoneValidAndAddToZones_DoesNothing_WhenCellIsNull()
+    {
+        Rules rules = new Rules();
+        Map map = new Map("background");
+        rules.IsZoneValidAndAddToZones(null, map);
+        Assert.Empty(map.Zones);
+    }
+
+    [Fact]
+    public void IsZoneValidAndAddToZones_DoesNothing_WhenCellValueIsNull()
+    {
+        Rules rules = new Rules();
+        Map map = new Map("background");
+        Cell cell = new Cell(0, 0);
+        rules.IsZoneValidAndAddToZones(cell, map);
+        Assert.Empty(map.Zones);
+    }
+
+    [Fact]
+    public void IsZoneValidAndAddToZones_AddsToExistingZone_WhenAdjacentCellWithSameValueExists()
+    {
+        Rules rules = new Rules();
+        Map map = new Map("background");
+        Cell cell = new Cell(0, 0);
+        cell.Value = 1;
+        Cell adjacentCell = new Cell(0, 1);
+        adjacentCell.Value = 1;
+        
+        map.Boards.Add(adjacentCell);
+        map.Zones.Add(new List<Cell> { adjacentCell });
+        
+        rules.IsZoneValidAndAddToZones(cell, map);
+        Assert.Contains(cell, map.Zones[0]);
+    }
+
+    [Fact]
+    public void IsZoneValidAndAddToZones_CreatesNewZone_WhenAdjacentCellWithSameValueExistsButNoExistingZone()
+    {
+        Rules rules = new Rules();
+        Map map = new Map("background");
+        Cell cell = new Cell(0, 0);
+        cell.Value = 1;
+        Cell adjacentCell = new Cell(0, 1);
+        adjacentCell.Value = 1;
+        
+        map.Boards.Add(adjacentCell);
+        rules.IsZoneValidAndAddToZones(cell, map);
+        Assert.Contains(cell, map.Zones[0]);
+    }
+}
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