Added tests

 - Added test that detects complete boxes
 - Added test that detects incomplete boxes
 - Added test that ensures box check occurs within game bounds
 - Added test that checks that horizontal and vertical lines are not duplicated
 - Added test that ensures lines are drawn within game bounds

src/test/java/dotsandboxes/DotsAndBoxesGridTest.java

 package dotsandboxes;
 
-import org.junit.jupiter.api.*;
 import static org.junit.jupiter.api.Assertions.*;
-import static org.junit.jupiter.api.Assumptions.*;
 
+import dotsandboxes.DotsAndBoxesGrid;
+import dotsandboxes.DotsAndBoxesUI;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.junit.jupiter.api.*;
 
 public class DotsAndBoxesGridTest {
+
   /*
    * Because Test classes are classes, they can have fields, and can have static fields.
    * This field is a logger. Loggers are like a more advanced println, for writing messages out to the console or a log file.
    */
-    private static final Logger logger = LogManager.getLogger(DotsAndBoxesGridTest.class);
+  private static final Logger logger = LogManager.getLogger(
+    DotsAndBoxesGridTest.class
+  );
 
   /*
    * Tests are functions that have an @Test annotation before them.
@@ -27,5 +31,103 @@ public class DotsAndBoxesGridTest {
     assertTrue(true);
   }
 
+  final int width = 5;
+  final int height = 5;
+
   // FIXME: You need to write tests for the two known bugs in the code.
+  @Test
+  public void boxCompleteDetectsCompletedBoxes() {
+    /*
+     * Box is complete
+     */
+    DotsAndBoxesGrid case1 = new DotsAndBoxesGrid(width, height, 2);
+    case1.drawHorizontal(0, 0, 0);
+    case1.drawVertical(0, 0, 1);
+    case1.drawHorizontal(0, 1, 0);
+    case1.drawVertical(1, 0, 1);
+    assertTrue(case1.boxComplete(0, 0));
+  }
+
+  @Test
+  public void boxCompleteDetectsIncompleteBoxes() {
+    /*
+     * Box is incomplete
+     */
+    DotsAndBoxesGrid case1 = new DotsAndBoxesGrid(width, height, 2);
+    case1.drawHorizontal(0, 0, 0);
+    case1.drawVertical(0, 0, 1);
+    case1.drawHorizontal(0, 1, 0);
+    assertFalse(case1.boxComplete(0, 0));
+  }
+
+  @Test
+  public void boxCompleteStaysWithinBounds() {
+    /*
+     * Box is within game board bounds
+     */
+    DotsAndBoxesGrid case1 = new DotsAndBoxesGrid(width, height, 2);
+    assertFalse(case1.boxComplete(-1, 0));
+    assertFalse(case1.boxComplete(width, 0));
+    assertFalse(case1.boxComplete(0, height));
+    assertFalse(case1.boxComplete(0, -1));
+  }
+
+  @Test
+  public void drawMethodsDetectRedrawnLines() {
+    DotsAndBoxesGrid case1 = new DotsAndBoxesGrid(width, height, 2);
+
+    /*
+     * Drawn lines are not duplicated
+     */
+
+    case1.drawHorizontal(0, 0, 0);
+
+    assertThrows(
+      RuntimeException.class,
+      () -> {
+        case1.drawHorizontal(0, 0, 0);
+      }
+    );
+
+    case1.drawVertical(0, 0, 0);
+
+    assertThrows(
+      RuntimeException.class,
+      () -> {
+        case1.drawVertical(0, 0, 0);
+      }
+    );
+
+    /*
+     * Drawn lines are within game board bounds
+     */
+
+    assertThrows(
+      RuntimeException.class,
+      () -> {
+        case1.drawHorizontal(-1, 0, 0);
+      }
+    );
+
+    assertThrows(
+      RuntimeException.class,
+      () -> {
+        case1.drawHorizontal(width, 0, 0);
+      }
+    );
+
+    assertThrows(
+      IndexOutOfBoundsException.class,
+      () -> {
+        case1.drawVertical(0, -1, 0);
+      }
+    );
+
+    assertThrows(
+      IndexOutOfBoundsException.class,
+      () -> {
+        case1.drawVertical(0, height, 0);
+      }
+    );
+  }
 }