Fixed Vector.cross and optimized the Vector tests slightly.

src/main/java/com/sk89q/worldedit/Vector.java

@@ -503,9 +503,9 @@ public class Vector {
      */
     public Vector cross(Vector other) {
         return new Vector(
-            y * other.z + z * other.y,
-            z * other.x + x * other.z,
-            x * other.y + y * other.x
+            y * other.z - z * other.y,
+            z * other.x - x * other.z,
+            x * other.y - y * other.x
         );
     }
 

src/test/java/com/sk89q/worldedit/VectorTest.java

@@ -100,16 +100,16 @@ public class VectorTest {
         final Vector b = new Vector(bx,by,bz);
         assertTrue(a.isCollinearWith(b));
         assertTrue(b.isCollinearWith(a));
-        assertTrue(a.multiply(-1).isCollinearWith(b));
-        assertTrue(a.isCollinearWith(b.multiply(-1)));
+        assertTrue(a.multiply(-1.0).isCollinearWith(b));
+        assertTrue(a.isCollinearWith(b.multiply(-1.0)));
     }
     private void assertNotCollinear(double ax, double ay, double az, double bx, double by, double bz) {
         final Vector a = new Vector(ax,ay,az);
         final Vector b = new Vector(bx,by,bz);
         assertFalse(a.isCollinearWith(b));
         assertFalse(b.isCollinearWith(a));
-        assertFalse(a.multiply(-1).isCollinearWith(b));
-        assertFalse(a.isCollinearWith(b.multiply(-1)));
+        assertFalse(a.multiply(-1.0).isCollinearWith(b));
+        assertFalse(a.isCollinearWith(b.multiply(-1.0)));
     }
 
     private void assertCollinear(double ax, double az, double bx, double bz) {
@@ -117,15 +117,15 @@ public class VectorTest {
         final Vector2D b = new Vector2D(bx,bz);
         assertTrue(a.isCollinearWith(b));
         assertTrue(b.isCollinearWith(a));
-        assertTrue(a.multiply(-1).isCollinearWith(b));
-        assertTrue(a.isCollinearWith(b.multiply(-1)));
+        assertTrue(a.multiply(-1.0).isCollinearWith(b));
+        assertTrue(a.isCollinearWith(b.multiply(-1.0)));
     }
     private void assertNotCollinear(double ax, double az, double bx, double bz) {
         final Vector2D a = new Vector2D(ax,az);
         final Vector2D b = new Vector2D(bx,bz);
         assertFalse(a.isCollinearWith(b));
         assertFalse(b.isCollinearWith(a));
-        assertFalse(a.multiply(-1).isCollinearWith(b));
-        assertFalse(a.isCollinearWith(b.multiply(-1)));
+        assertFalse(a.multiply(-1.0).isCollinearWith(b));
+        assertFalse(a.isCollinearWith(b.multiply(-1.0)));
     }
 }