Add tests to check exception is thrown when line already drawn.

Add test to check box is complete.

src/main/java/dotsandboxes/LineAlreadyDrawnException.java

+package dotsandboxes;
+import java.lang.Exception;
+
+public class LineAlreadyDrawnException extends Exception{}
\ No newline at end of file

src/test/java/dotsandboxes/DotsAndBoxesGridTest.java

@@ -21,11 +21,48 @@ public class DotsAndBoxesGridTest {
      *
      * This is a dummy test just to show that the test suite itself runs
      */
+    
+
+    // FIXME: You need to write tests for the two known bugs in the code.
     @Test
-    public void testTestSuiteRuns() {
-        logger.info("Dummy test to show the test suite runs");
-        assertTrue(true);
+    public void testExisitingHorizontalLineThrowsException() {
+      DotsAndBoxesGrid dbg = new DotsAndBoxesGrid(4, 3, 2);
+          dbg.drawHorizontal(0, 0, 0);
+        assertThrows(LineAlreadyDrawnException.class, () -> {dbg.drawHorizontal(0, 0, 0);});
     }
 
-    // FIXME: You need to write tests for the two known bugs in the code.
+    @Test
+    public void testExisitingVerticalLineThrowsException() {
+      DotsAndBoxesGrid dbg = new DotsAndBoxesGrid(4, 3, 2);
+          dbg.drawVertical(0, 0, 0);
+        assertThrows(LineAlreadyDrawnException.class, () -> {dbg.drawVertical(0, 0, 0);});
+    }
+ 
+    @Test
+    public void testOutOfBoundsHorizontalLineThrowsException() {
+      DotsAndBoxesGrid dbg = new DotsAndBoxesGrid(4, 3, 2);
+         
+        assertThrows(IndexOutOfBoundsException.class, () -> {dbg.drawHorizontal(4, 0, 0);});
+    }
+
+
+
+    @Test
+    public void testBoxComplete() {
+        DotsAndBoxesGrid dbg = new DotsAndBoxesGrid(4, 3, 2);
+        assertEquals(dbg.boxComplete(0,0),false);
+        dbg.drawHorizontal(0,0,0);
+        assertEquals(dbg.boxComplete(0,0),false);
+        dbg.drawVertical(0,0,0);
+        assertEquals(dbg.boxComplete(0,0),false);
+        dbg.drawVertical(1,0,0);
+        assertEquals(dbg.boxComplete(0,0),false);
+        dbg.drawHorizontal(0,1,0);
+        assertEquals(dbg.boxComplete(0,0),true);
+
+    }
+
+
+
+
 }