We should check that all writes succeed in where4.js, in order to make build failures more diagnosable. Additionally, we can make the following improvements to the test:

1) Make the test use its own database, to prevent conflict with other tests that use the system.js collection.

2) Remove the insertion and deletion of {_id: "w4", value: "5"} in the system.js collection, since it serves no clear purpose.

3) Instead of deleting {_id: "where4_equalsOne"} from the system.js collection, delete {_id: "where4_addOne"}, since this is the function that was added.