Refactor existing performance test

[hectorjsmith]

Requirement

Refactor the existing performance test (TestGivenArrayWithLargeNumberOfElementsWhenCheckForDuplicatesThenCheckIsFast) to ensure its result is deterministic and not based on chance.

Another option is to simply remove this test.

Once this test is resolved, test categories can be removed from all other tests. Since all other tests have the same category the categories serve no purpose.

Value Proposition

There are two main issues with the existing performance test:

1. It is a manual test - This means the user has to manually inspect the output of the test
2. Its result can vary based on factors not related to the code itself (e.g. the processing speed of the machine it runs on)

Design Ideas

The simplest solution is to remove the test. But there may be value in having this test to ensure that performance does not suffer.

If the test is to stay, it should be refactored to fix the two issues above.

This issue requires further discussion