Add unit test about long context

[AsakusaRinne]

Description

Sometimes unexpected behaviors might appear when the conversation is very long. We need to add unit test for it.

[Shampy05]

I'd like to work on this issue, if possible. Thanks.

[AsakusaRinne]

Sure, assigned this issue to you. Thank you for the contribution!

[martindevans]

Note that any tests added for this probably need to be disabled on CI, the runner don't have the memory or the compute to handle long contexts!