Account for input data size in memory hook test without inline cupy array copy

[yousefmoazzam]

Fixes #512

If one is wondering how these changes could possibly fix the issue, see the message of b153411

Checklist

• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] I have made corresponding changes to the documentation