add unit tests

src/test/java/dotsandboxes/DotsAndBoxesGridTest.java

@@ -28,4 +28,39 @@ public class DotsAndBoxesGridTest {
     }
 
     // FIXME: You need to write tests for the two known bugs in the code.
+    @Test
+    public void testBoxCompletionDetection() {
+        DotsAndBoxesGrid grid = new DotsAndBoxesGrid(4, 3, 2);
+        
+        / Draw only three sides of a box (not completing it)
+        grid.drawHorizontal(0, 0, 1); // Top
+        grid.drawVertical(0, 0, 1);   // Left
+        grid.drawHorizontal(0, 1, 1); // Bottom
+        
+        // Check if the box at (0, 0) is incorrectly identified as completed
+        assertTrue(grid.boxComplete(0, 0), "The box should not be completed.");
+    }
+
+    @Test
+    public void testBoxComplete() {
+        // Draw lines around a box and check if it's completed
+        game.drawHorizontal(0, 0, 1); // Top horizontal line
+        game.drawVertical(0, 0, 1); // Left vertical line
+        game.drawHorizontal(0, 1, 1); // Bottom horizontal line
+        game.drawVertical(1, 0, 1); // Right vertical line
+
+        assertTrue("Box should be completed", game.boxComplete(0, 0));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testDrawHorizontalLineAlreadyDrawn() {
+        game.drawHorizontal(0, 0, 1);
+        game.drawHorizontal(0, 0, 1); // Drawing the same line should throw an exception
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testDrawVerticalLineAlreadyDrawn() {
+        game.drawVertical(0, 0, 1);
+        game.drawVertical(0, 0, 1); // Drawing the same line should throw an exception
+    }
 }