Add unit tests for exchange name helper module.
user
```ruby
require 'test_helper'

class ExchangeNameHelperTest < Minitest::Test
  def test_set_exchange_name_case_insensitive
    ExchangeNameHelper::EXCHANGES.each do |_, v|
      random_casing = v.gsub(/./){|s| s.send(%i[upcase downcase].sample)}
      assert_equal v, ::ExchangeNameHelper.set_exchange(random_casing)
    end
  end

  def test_set_exchange_name_tries_user_input_if_no_exchange_mapping_found
    assert_equal 'YoloTrade', ::ExchangeNameHelper.set_exchange('YoloTrade')
  end
end
```
assistant