Unit tests added to test errors in the code.

src/test/java/dotsandboxes/DotsAndBoxesGridTest.java

@@ -27,5 +27,26 @@ public class DotsAndBoxesGridTest {
         assertTrue(true);
     }
 
+    @Test
+    public void testGridComplete()
+    {
+        DotsAndBoxesGrid testGrid = new DotsAndBoxesGrid(5,5,1);
+
+        testGrid.drawHorizontal(1,1,1);
+        testGrid.drawHorizontal(1,2,1);
+        testGrid.drawVertical(1,1,1);
+
+        assertFalse(testGrid.boxComplete(1,1),"Box is not Complete");
+    }
+
+    @Test
+    public void testLineDrawn()
+    {
+
+        DotsAndBoxesGrid testGrid2 = new DotsAndBoxesGrid(5,5,1);
+
+        testGrid2.drawVertical(1,1,1);
+        assertThrows(IllegalArgumentException.class, () ->testGrid2.drawVertical(1,1,1), "Line already Drawn");
+    }
     // FIXME: You need to write tests for the two known bugs in the code.
 }