Refactor tests

src/Vector3.java

@@ -22,6 +22,10 @@ public class Vector3 {
         this.z = z;
     }
 
+    public Vector3(Vector3 other) {
+        this(other.x, other.y, other.z);
+    }
+
     /**
      * Returns the sum of this vector and vector 'v'.
      */