### Question:
CostManagementImpl implements CostManagementService { @Override public CommonResult deleteCostById(Integer id){ if (costMapper.get(id) == null) { return CommonResult.fail(E_602); } int count = costMapper.delete(id); if (count == 0) { return CommonResult.fail(); } return CommonResult.success(count); }  @Override CommonResult listAllCosts(); @Override CommonResult getCostById(Integer id); @Override CommonResult insertCost(Cost cost); @Override CommonResult updateCostById(Cost cost); @Override CommonResult deleteCostById(Integer id);  }### Answer:
@Test public void testDeleteCostById() throws Exception { }