anchor.diff:        flameTester.test(
           'limits enabled',
           (game) async {
  +          await game.ensureAddAll([plunger, anchor]);
  +
             final jointDef = PlungerAnchorPrismaticJointDef(
               plunger: plunger,
               anchor: anchor,
  
positive.code:       flameTester.test(
          'lower translation limit as negative infinity',
          (game) async {
            final jointDef = PlungerAnchorPrismaticJointDef(
              plunger: plunger,
              anchor: anchor,
  
negative.code:       flameTester.test(
          'anchor as bodyB',
          (game) async {
            await game.ensureAddAll([plunger, anchor]);
  
            final jointDef = PlungerAnchorPrismaticJointDef(
              plunger: plunger,
              anchor: anchor,
  