Issue 1 bugfix - fixed the two known bugs; All the unit tests now pass successfully.

src/main/java/dotsandboxes/DotsAndBoxesGrid.java

@@ -113,7 +113,16 @@ public class DotsAndBoxesGrid {
 
         // A box is complete if the north and south horizontals and the east and west verticals have all been drawn.
         // FIXME: You'll need to fix this code (after writing a test first).
-        return true;
+
+        // set boolean
+        boolean isTheBoxComplete = false;
+
+        // Check if all four lines that complete the box are drawn
+        if(verticals[x][y] == true && horizontals[x][y] == true &&
+                verticals[x+1][y] == true && horizontals[x][y+1] == true){
+            isTheBoxComplete = true;
+        }
+        return isTheBoxComplete;
     }
 
     /** Tries to claim a box for a player. If the box is complete, sets the ownership and returns true. */
@@ -142,6 +151,13 @@ public class DotsAndBoxesGrid {
 
         // FIXME: You need to throw an exception if the line was already drawn.
 
+        // Throws an 'illegalStateException' when an attempt is made to draw a
+        // horizontal line that's already been drawn.
+        if (horizontals[x][y]){
+                throw new IllegalStateException(
+                        String.format("A horizontal line is already drawn at x: %d & y: %d", x,y));
+        }
+
         this.horizontals[x][y] = true;
 
         // Try to claim the north or south boxes
@@ -173,6 +189,13 @@ public class DotsAndBoxesGrid {
 
         // You need to throw an exception if the line was already drawn.
 
+        // Throws an 'illegalStateException' when an attempt is made to draw a
+        // vertical line that's already been drawn.
+        if (verticals[x][y]){
+            throw new IllegalStateException(
+                    String.format("A vertical line is already drawn at x: %d & y: %d", x,y));
+        }
+
         this.verticals[x][y] = true;
         // Try to claim the north or south boxes
         boolean claimE = claimBox(x, y, player);