feat: improve test coverage

Author: sailok.chinta

src/test/java/com/thealgorithms/datastructures/trees/QuadTreeTest.java

@@ -9,6 +9,11 @@ public class QuadTreeTest {
     BoundingBox boundingBox = new BoundingBox(new Point(0, 0), 500);
     QuadTree quadTree = new QuadTree(boundingBox, quadTreeCapacity);
 
+    @Test
+    public void testNullPointInsertIntoQuadTree() {
+        Assertions.assertFalse(quadTree.insert(null));
+    }
+
     @Test
     public void testInsertIntoQuadTree() {
         Assertions.assertTrue(quadTree.insert(new Point(10, -10)));
@@ -18,12 +23,28 @@ public void testInsertIntoQuadTree() {
         Assertions.assertFalse(quadTree.insert(new Point(1050, 1050)));
     }
 
+    @Test
+    public void testInsertIntoQuadTreeAndSubDivide() {
+        Assertions.assertTrue(quadTree.insert(new Point(10, -10)));
+        Assertions.assertTrue(quadTree.insert(new Point(-10, 10)));
+        Assertions.assertTrue(quadTree.insert(new Point(-10, -10)));
+        Assertions.assertTrue(quadTree.insert(new Point(10, 10)));
+        Assertions.assertTrue(quadTree.insert(new Point(-100, 100)));
+        Assertions.assertTrue(quadTree.insert(new Point(100, -100)));
+        Assertions.assertTrue(quadTree.insert(new Point(-100, -100)));
+        Assertions.assertTrue(quadTree.insert(new Point(100, 100)));
+    }
+
     @Test
     public void testQueryInQuadTree() {
         quadTree.insert(new Point(10, -10));
         quadTree.insert(new Point(-10, 10));
         quadTree.insert(new Point(-10, -10));
         quadTree.insert(new Point(10, 10));
+        quadTree.insert(new Point(-100, 100));
+        quadTree.insert(new Point(100, -100));
+        quadTree.insert(new Point(-100, -100));
+        quadTree.insert(new Point(100, 100));
 
         List<Point> points = quadTree.query(new BoundingBox(new Point(0, 0), 100));
         Assertions.assertEquals(4, points.size());