Make successful non-defaulting onCreate integration tests less verbose

[mdbooth]

We have a great deal of onCreate tests which expect the object to be created exactly as specified without modification. We currently require these tests to specify identical values for initial and expected. In the common case where they are identical, this makes the tests more error-prone to write and validate visually. It would be simpler if it were permitted to omit one of these values if it should be identical to the other.

I recommend that we allow expected to be omitted. If omitted, we default it to the value of initial.

Similarly for onUpdate tests, we could default the value of expected to the value of updated.

[JoelSpeed]

#2541 (comment)

Per comment on the implementation, we would like to keep the expected as an explicit test option and not default it for now