Add Chooser component unit tests

[alessandrodolci]

Fixes #33

Description
I implemented unit tests for the component trying to follow your approach, based on other components' tests.
This should cover all the main aspects of the code, I'll try to further expand it if something comes to my mind. Of course, feel free to ask if you think it's not enough or something's wrong, I'd be glad to continue helping.

Checklist:

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the master branch of the repository.
• My commit messages follow best practices.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

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[akmadian]

Looks great @alessandrodolci! Merging now :)

[alessandrodolci]

Thank you, really glad to have helped!