Extend the e2e tests with append a partitioned file

[Fokko]

As a follow-up for #349.

We should add another test for adding a partitioned file.

[feniljain]

Heyo! 👋🏻

I see main PR is approved and in good shape, I would love to take a stab at this! :)

[Fokko]

@feniljain Thanks, I've merged the PR. I always want to give others the chance to chime in as well.