Updated code so that boxComplete, drawHorizontal and drawVertical methods pass unit tests

src/main/java/dotsandboxes/DotsAndBoxesGrid.java

@@ -109,8 +109,9 @@ public class DotsAndBoxesGrid {
     public boolean boxComplete(int x, int y) {
         if (x >= width - 1 || x < 0 || y >= height - 1 || y < 0) {
             return false;
+        } else if ((!this.getHorizontal(x,y)) || (!this.getVertical(x,y)) || (!this.getHorizontal(x+1,y)) || (!this.getVertical(x,y+1))) {
+            return false;
         }
-
         // 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;
@@ -139,7 +140,9 @@ public class DotsAndBoxesGrid {
         if (y >= height || y < 0) {
             throw new IndexOutOfBoundsException(String.format("y was %d, which is out of range. Range is 0 to %d", y, height));
         }
-
+        if (this.getHorizontal(x,y)) {
+            throw new IllegalStateException("That line has already been taken");
+        }
         // FIXME: You need to throw an exception if the line was already drawn.
 
         this.horizontals[x][y] = true;
@@ -170,7 +173,9 @@ public class DotsAndBoxesGrid {
         if (y >= height - 1 || y < 0) {
             throw new IndexOutOfBoundsException(String.format("y was %d, which is out of range. Range is 0 to %d", y, height - 1));
         }
-
+        if (this.getVertical(x,y)) {
+            throw new IllegalStateException("That line has already been taken");
+        }
         // You need to throw an exception if the line was already drawn.
 
         this.verticals[x][y] = true;