我是单元测试领域的初学者，所以我有一些问题：
返回 DataTable 的方法是一个好的做法吗？如果是，那么我该如何测试它？
这是他们要求我测试的一个函数：
public static DataTable GeneratePeriods(DateTime startDate, DateTime endDate, string periodicity)
{
try
{
using (DataTable periods = new DataTable())
{
periods.Columns.Add(new DataColumn("Dates", typeof(DateTime)));
int startYear = startDate.Year;
int endYear = endDate.Year;
int Diff = endYear - startYear + 1;
int LoopYear;
/* This generates all regular periods from the begin date to the end date */
switch (periodicity)
{
//monthly
case "Mensuelle":
for (int j = 0; j < Diff; j++)
{
LoopYear = startYear + j;
for (int i = 1; i <= 12; i++)
if (i != 12)
periods.Rows.Add(new DateTime(LoopYear, i + 1, 1).AddDays(-1));
else
periods.Rows.Add(new DateTime(LoopYear, 12, 31));
}
break;
//quarterly
case "Trimestrielle":
for (int j = 0; j < Diff; j++)
{
LoopYear = startYear + j;
for (int i = 1; i <= 4; i++)
if (i != 4)
periods.Rows.Add(new DateTime(LoopYear, (i * 3) + 1, 1).AddDays(-1));
else
periods.Rows.Add(new DateTime(LoopYear, 12, 31));
}
break;
//biannual
case "Semestrielle":
for (int j = 0; j < Diff; j++)
{
LoopYear = startYear + j;
for (int i = 1; i <= 2; i++)
if (i != 2)
periods.Rows.Add(new DateTime(LoopYear, (i * 6) + 1, 1).AddDays(-1));
else
periods.Rows.Add(new DateTime(LoopYear, 12, 31));
}
break;
//annual
case "Annuelle":
for (int j = 0; j < Diff; j++)
{
LoopYear = startYear + j;
for (int i = 1; i <= 1; i++)
periods.Rows.Add(new DateTime(LoopYear, 12, 31));
}
break;
}
//this adds startDate in periods datatable if it doesn't exist
if (periods.Select(String.Format("Dates = '{0}'", startDate)).Length == 0)
periods.Rows.Add(startDate);
//this adds endDate date in periods datatable if it doesn't exist
if (periods.Select(String.Format("Dates = '{0}'", endDate.AddDays(-1))).Length == 0)
periods.Rows.Add(endDate);
//this removes all date ranges below the startDate
DataRow[] dr = periods.Select(String.Format("Dates < '{0}'", startDate));
foreach (DataRow row in dr)
periods.Rows.Remove(row);
//this removes all date ranges above the endDate
DataRow[] dr1 = periods.Select(String.Format("Dates >'{0}'", endDate.AddDays(-1)));
foreach (DataRow row in dr1)
periods.Rows.Remove(row);
//this adds endDate date in periods datatable if it doesn't exist for the second time ! (I personnaly don't know why it's duplicated but it dosen't work without this =) )
if (periods.Select(String.Format("Dates = '{0}'", endDate.AddDays(-1))).Length == 0)
periods.Rows.Add(endDate);
DataView dv = new DataView(periods) { Sort = "Dates ASC" };
// this initialize a new datatable with sorted dates
DataTable dt_dates = dv.ToTable();
// this initialize a new datatable
DataTable dt_periods = new DataTable();
dt_periods.Columns.Add("Periods", typeof(string));
dt_periods.Columns.Add("NombreJours", typeof(int));
// this loop creates period ranges shown to the user (Du startDate au endDate)
DateTime dateDebutPeriode;
DateTime dateFinPeriode;
int NombreJours;
for (int i = 0; i < dv.Table.Rows.Count - 1; i++)
if (i == 0)
{
dateDebutPeriode = DateTime.Parse(dt_dates.Rows[i]["Dates"].ToString());
dateFinPeriode = DateTime.Parse(dt_dates.Rows[i + 1]["Dates"].ToString());
NombreJours = dateFinPeriode.Subtract(dateDebutPeriode).Days + 1;
dt_periods.Rows.Add(String.Format("Du {0} au {1}", dateDebutPeriode.ToShortDateString(), dateFinPeriode.ToShortDateString()), NombreJours);
}
else
if (i == dv.Table.Rows.Count - 2)
{
dateDebutPeriode = DateTime.Parse(dt_dates.Rows[i]["Dates"].ToString()).AddDays(1);
dateFinPeriode = DateTime.Parse(dt_dates.Rows[i + 1]["Dates"].ToString()).AddDays(-1);
NombreJours = dateFinPeriode.Subtract(dateDebutPeriode).Days + 1;
dt_periods.Rows.Add(String.Format("Du {0} au {1}", dateDebutPeriode.ToShortDateString(), dateFinPeriode.ToShortDateString()), NombreJours);
}
else
{
dateDebutPeriode = DateTime.Parse(dt_dates.Rows[i]["Dates"].ToString()).AddDays(1);
dateFinPeriode = DateTime.Parse(dt_dates.Rows[i + 1]["Dates"].ToString());
NombreJours = dateFinPeriode.Subtract(dateDebutPeriode).Days + 1;
dt_periods.Rows.Add(String.Format("Du {0} au {1}", dateDebutPeriode.ToShortDateString(), dateFinPeriode.ToShortDateString()), NombreJours);
}
return dt_periods;
}
}
catch (InvalidOperationException)
{
throw;
}
}