[ENH] Improve test coverage of similarity search module

[baraline]

Describe the feature or idea you want to propose

Some search options are currently not covered by testing, such as the apply_exclusion_to_result parameter during predict.

Describe your proposed solution

Implement more test to cover all the use cases.

Describe alternatives you've considered, if relevant

No response

Additional context

No response

[TonyBagnall]

code missed