Bugs now fixed and all tests passed

src/main/java/dotsandboxes/DotsAndBoxesGrid.java

@@ -113,7 +113,7 @@ 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;
+        else return (this.getHorizontal(x, y)) && (this.getVertical(x, y)) && (this.getHorizontal(x, y + 1)) && (this.getVertical(x + 1, y));
     }
 
     /** Tries to claim a box for a player. If the box is complete, sets the ownership and returns true. */
@@ -141,6 +141,9 @@ public class DotsAndBoxesGrid {
         }
 
         // FIXME: You need to throw an exception if the line was already drawn.
+        if (this.horizontals[x][y]) {
+            throw new IllegalStateException("Sorry string has already been drawn here");
+        }
 
         this.horizontals[x][y] = true;
 
@@ -172,7 +175,9 @@ public class DotsAndBoxesGrid {
         }
 
         // You need to throw an exception if the line was already drawn.
-
+        if (this.verticals[x][y]) {
+            throw new IllegalStateException("Sorry string has already been drawn here");
+        }
         this.verticals[x][y] = true;
         // Try to claim the north or south boxes
         boolean claimE = claimBox(x, y, player);