Added test for the class Tree

src/test/java/inf112/skeleton/app/TreeTest.java

+package inf112.skeleton.app;
+import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.*;
+
+public class TreeTest{
+	Tree tree;
+	@BeforeEach
+	void setup() {
+		this.tree = new Tree(0, 0, 200, 230);
+	}
+	
+    @Test
+	void TestgetHeight() {
+	    assertEquals(tree.getHeight(), 230);
+	}
+	@Test
+	void TestgetWidth() {
+		assertEquals(tree.getWidth(), 200);
+	}
+	@Test
+	void TestgetX() {
+		assertEquals(tree.getX(), 0);
+	}
+	@Test
+	void getY() {
+	    assertEquals(tree.getY(), 0);
+	}
+	@Test
+	void getSpeed() {
+		assertEquals(tree.getSpeed(), 0);
+	}
+	@Test
+	void getGravity() {
+	    assertEquals(tree.getGravity(), 5);
+	}
+}