Added Unit Tests that detect the errors in the code

src/test/java/dotsandboxes/DotsAndBoxesGridTest.java

@@ -19,13 +19,51 @@ public class DotsAndBoxesGridTest {
      * The typical format of a test is that it contains some code that does something, and then one
      * or more assertions to check that a condition holds.
      *
-     * This is a dummy test just to show that the test suite itself runs
      */
+    
+     // Unit test to determine if the boxComplete algorithm correctly discerns a box is complete
+     // This test is currently vacuously true - it's not failing but that isn't indicative of 
+     // the algorithm working - the function simply always returns true for values of x and y where
+     // 0 < x < width-1 OR 0 < y < height-1
     @Test
-    public void testTestSuiteRuns() {
-        logger.info("Dummy test to show the test suite runs");
-        assertTrue(true);
-    }
+    public void testBoxIsComplete() {
+        // test against box that is known to be complete
+        DotsAndBoxesGrid test1 = new DotsAndBoxesGrid(4, 4, 2);
+        test1.drawHorizontal(0, 0, 0);
+        test1.drawVertical(0, 0, 1);
+        test1.drawHorizontal(0, 1, 0);  
+        test1.drawVertical(1, 0, 1);
+        assertTrue(test1.boxComplete(0, 0));
+        }
+
+    // Unit test to determine if the boxComplete correctly discerns a box is not complete
+    @Test 
+    public void testBoxIsNotComplete() {
+        // test against 'box' that is known to not be complete
+        DotsAndBoxesGrid test2 = new DotsAndBoxesGrid(6, 6, 2);
+        test2.drawHorizontal(0, 0, 0);
+        test2.drawVertical(0, 0, 1);
+        test2.drawHorizontal(2, 0, 0);  
+        test2.drawVertical(2, 0, 1);
+        assertFalse(test2.boxComplete(0, 0));
+    }   
 
-    // FIXME: You need to write tests for the two known bugs in the code.
+    // Unit test to determine if the horizontal draw function permits you to draw over a line that has already been drawn
+    @Test
+    public void testHorizontalLineAlreadyDrawn() {
+        DotsAndBoxesGrid test = new DotsAndBoxesGrid(5, 5, 2);
+        test.drawHorizontal(1, 0, 0);
+        assertThrows(IllegalStateException.class, () -> {
+            test.drawHorizontal(1, 0, 0); 
+          });
+    }
+    // Unit test to determine if the vertical draw function permits you to draw over a line that has already been drawn
+    @Test
+    public void testVerticalLineAlreadyDrawn() {
+        DotsAndBoxesGrid test = new DotsAndBoxesGrid(5, 5, 2);
+        test.drawVertical(1, 0, 0);
+        assertThrows(IllegalStateException.class, () -> {
+            test.drawVertical(1, 0, 0); 
+          });
+    }
 }