diff --git a/source/Trek-12/Tests/RulesTests.cs b/source/Trek-12/Tests/RulesTests.cs
index 2994420..3b6fe48 100644
--- a/source/Trek-12/Tests/RulesTests.cs
+++ b/source/Trek-12/Tests/RulesTests.cs
@@ -28,6 +28,16 @@ public class RulesTests
         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()
     {
@@ -36,4 +46,31 @@ public class RulesTests
         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));
+    }
 }
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