@accessors(copy) had no test in ./Tests.
The compiler's copy-accessor setter behaviour was unverified.
Add CopyAccessorTest.j to Tests/Objective-J. It asserts three
properties of the generated setter:
- the stored value is not identical to the assigned object
- the stored value is unaffected by later mutation of the original
- the stored value is equal in content to the original at assignment
This is added both as a matter of good coverage for the existing toolchain and so that new tooling has a reference for a piece of foundational behaviour.
