improve finder spec

spec/finders/users_finder_spec.rb

@@ -63,11 +63,14 @@ describe UsersFinder do
       end
 
       it 'filters by created_at' do
+        filtered_user_before = create(:user, created_at: 3.days.ago)
+        filtered_user_after = create(:user, created_at: Time.now + 3.days)
+
         users = described_class.new(user,
                                     created_after: 2.days.ago,
                                     created_before: Time.now + 2.days).execute
 
-        expect(users.count).to eq(4)
+        expect(users.map(&:username)).not_to include([filtered_user_before.username, filtered_user_after.username])
       end
     end