fixed duplicate line and complete box bugs

src/main/java/dotsandboxes/DotsAndBoxesGrid.java

@@ -113,7 +113,10 @@ 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;
+        if (this.horizontals[x][y] && this.horizontals[x][y + 1] && this.verticals[x][y] && this.verticals[x + 1][y]) {
+            return true;
+        }
+        return false;
     }
 
     /** Tries to claim a box for a player. If the box is complete, sets the ownership and returns true. */
@@ -140,7 +143,10 @@ public class DotsAndBoxesGrid {
             throw new IndexOutOfBoundsException(String.format("y was %d, which is out of range. Range is 0 to %d", y, height));
         }
 
-        // FIXME: You need to throw an exception if the line was already drawn.
+        // Throw an exception if the line was already drawn.
+        if (this.horizontals[x][y]) {
+            throw new IllegalStateException("This line has already been drawn");
+        }
 
         this.horizontals[x][y] = true;
 
@@ -171,7 +177,10 @@ public class DotsAndBoxesGrid {
             throw new IndexOutOfBoundsException(String.format("y was %d, which is out of range. Range is 0 to %d", y, height - 1));
         }
 
-        // You need to throw an exception if the line was already drawn.
+        // Throw an exception if the line was already drawn.
+        if (this.verticals[x][y]) {
+            throw new IllegalStateException("This line has already been drawn");
+        }
 
         this.verticals[x][y] = true;
         // Try to claim the north or south boxes

src/test/java/dotsandboxes/DotsAndBoxesGridTest.java

@@ -17,7 +17,7 @@ public class DotsAndBoxesGridTest {
 
     /*
     * A test to check if a box is correctly marked as complete.
-    * Asserting False after drawing a complete box
+    * Asserting True after drawing a complete box
     */
 
 
@@ -31,13 +31,13 @@ public class DotsAndBoxesGridTest {
         grid.drawVertical(1,1,1);
         grid.drawVertical(2,1,1);
 
-        assertFalse(grid.boxComplete(1, 1));
+        assertTrue(grid.boxComplete(1, 1));
     }
 
 
     /*
     * A test to see if a line can be redrawn after it has already been drawn,
-    * test should throw an exception
+    * test should throw an exception.
     */
     @Test
     public void testRedrawLineFails() {