minor #205 [Agent] Add unit tests for Agent (OskarStark)

This PR was squashed before being merged into the main branch.

Discussion
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[Agent] Add unit tests for `Agent`

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| Docs?         | no
| Issues        | --
| License       | MIT

Commits
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bba8e46 [Agent] Add unit tests for `Agent`

Author: chr-hertel