How can I pass dynamic objects into an NUnit TestCase function?

Question

I am writing a data-intensive application. I have the following tests. They work, but they're pretty redundant.

[Test]
public void DoSanityCheck_WithCountEqualsZeroAndHouseGrossIsGreater_InMerchantAggregateTotals_SetsWarning()
{
    report.Merchants[5461324658456716].AggregateTotals.ItemCount = 0;
    report.Merchants[5461324658456716].AggregateTotals._volume = 0;
    report.Merchants[5461324658456716].AggregateTotals._houseGross = 1;

    report.DoSanityCheck();

    Assert.IsTrue(report.FishyFlag);
    Assert.That(report.DataWarnings.Where(x=> x is Reports.WarningObjects.ImbalancedVariables && x.mid == 5461324658456716 && x.lineitem == "AggregateTotals").Count() > 0);
}


[Test]
public void DoSanityCheck_WithCountEqualsZeroAndHouseGrossIsGreater_InAggregateTotals_SetsWarning()
{
    report.AggregateTotals.ItemCount = 0;
    report.AggregateTotals._volume = 0;
    report.AggregateTotals._houseGross = 1;

    report.DoSanityCheck();

    Assert.IsTrue(report.FishyFlag);
    Assert.That(report.DataWarnings.Where(x=> x is Reports.WarningObjects.ImbalancedVariables && x.mid == null && x.lineitem == "AggregateTotals").Count() > 0);
}


[Test]
public void DoSanityCheck_WithCountEqualsZeroAndHouseGrossIsGreater_InAggregateTotalsLineItem_SetsWarning()
{
    report.AggregateTotals.LineItem["WirelessPerItem"].ItemCount = 0;
    report.AggregateTotals.LineItem["WirelessPerItem"]._volume = 0;
    report.AggregateTotals.LineItem["WirelessPerItem"]._houseGross = 1;

    report.DoSanityCheck();

    Assert.IsTrue(report.FishyFlag);
    Assert.That(report.DataWarnings.Where(x=> x is Reports.WarningObjects.ImbalancedVariables && x.mid == null && x.lineitem == "WirelessPerItem").Count() > 0);
}

The same properties are modified at the beginning, just as children of different container objects, and a couple of values in the assertion change at the end.

I need to write a few dozen of these, checking different properties. So I want to parameterize the test. The trick is passing the container object as a parameter to the test. The container object is instantiated in the test fixture SetUp.

I want to achieve something like this:

[TestCase(report.AggregateTotals.LineItem["WirelessPerItem"], 0, "WirelessPerItem")]
[TestCase(report.AggregateTotals, 4268435971532164, "AggregateTotals")]
[TestCase(report.Merchants[5461324658456716].AggregateTotals, 5461324658456716, "WirelessPerItem")]
[TestCase(report.Merchants[4268435971532164].LineItem["EBTPerItem"], 4268435971532164, "EBTPerItem")]
public void DoSanityCheck_WithCountEqualsZeroAndHouseGrossIsGreater_TestCase_SetsWarning(object container, long mid, string field)
{
    container.ItemCount = 0;
    container._volume = 0;
    container._houseGross = 1;

    report.DoSanityCheck();

    Assert.IsTrue(report.FishyFlag);
    Assert.That(report.DataWarnings.Where(x=> x is Reports.WarningObjects.ImbalancedVariables && x.mid == mid && x.lineitem == field).Count() > 0);
}

But that doesn't work and I'm not sure how to make it work, or if it's possible.

Answer 1

I tracked it down. I can't pass an instantiated object into a test via TestCase because attributes are strictly for static meta-data. But the NUnit team has a solution for that, TestCaseSource. The post on the NUnit list that answered the question is here.

Here is what my solution now looks like:

public static IEnumerable<TestCaseData> CountEqualsZeroAndHouseGrossIsGreaterTestCases
{
    get
    {
        yield return new TestCaseData(report, report.Merchants[4268435971532164].LineItem["EBTPerItem"], 4268435971532164, "EBTPerItem").SetName("ReportMerchantsLineItem");
        yield return new TestCaseData(report, report.Merchants[5461324658456716].AggregateTotals, 5461324658456716, "WirelessPerItem").SetName("ReportMerchantsAggregateTotals");
        yield return new TestCaseData(report, report.AggregateTotals, null, "AggregateTotals").SetName("ReportAggregateTotals");
        yield return new TestCaseData(report, report.AggregateTotals.LineItem["WirelessPerItem"], null, "WirelessPerItem").SetName("ReportAggregateTotalsLineItem");
    }
}


[TestCaseSource("CountEqualsZeroAndHouseGrossIsGreaterTestCases")]
public void DoSanityCheck_WithCountEqualsZeroAndHouseGrossIsGreater_TestCase_SetsWarning(Reports.ResidualsReport report, Reports.LineItemObject container, long? mid, string field)
{
    container.ItemCount = 0;
    container._volume = 0;
    container._houseGross = 1;

    report.DoSanityCheck();

    Assert.IsTrue(report.FishyFlag);
    Assert.That(report.DataWarnings.Where(x=> x is Reports.WarningObjects.ImbalancedVariables && x.mid == mid && x.lineitem == field).Count() > 0);
}

It is not as pretty as I hoped and is not as easy to read. But it did succeed on cutting down code duplication, which should make things easier to maintain and fix.