Extend test_store_create_delete_get()
Extend test_store_create_delete_get()

to actually test:

1. get      -> Should return Ok(None)
2. create   -> Should return Ok(())
3. get      -> Should return Ok(Some(_))
4. delete   -> Should return Ok(())
5. get      -> Should return Ok(None)

mario-kr/imag,mario-kr/imag,matthiasbeyer/imag,matthiasbeyer/imag