@Test
public void should_find_team_with_the_smallest_goal_difference_in_football_league() throws IOException {

    List<TeamResult> footballLeagueResults = newArrayList(
            new TeamResult("Arsenal", 79, 36),
            new TeamResult("Liverpool", 67, 30));
    doReturn(footballLeagueResults).when(footballFileReader).readFile();
    Optional<String> teamWithMinimumGoalDifference = smallestGoalDifference.teamWithMinimumGoalDifference();
    assertThat(teamWithMinimumGoalDifference).hasValue("Liverpool");
}