Nick Sertis

TDD: Comparing Datasets

I’ve been writing some unit tests today to make sure that my code fetches the correct DataSet from the database. I wanted to test that the DataSet returned by the data layer matches the DataSet that I expect, so I used the following Assert statement:

Assert.AreEqual(expectedDataSet, actualDataSet);

When I ran this test on two empty DataSets it failed with this helpful message:

NUnit.Framework.AssertionException:
Expected: <system.Data.DataSet>
But was:  <system.Data.DataSet>

That suggests that while the structure and data inside two DataSets are the same, there is a fundamental difference in the objects that means you cannot compare them in this way.

It turns out that there is a quick and easy way to compare two DataSets if you want to ensure that they’re identical. Here it is:

Assert.AreEqual(expectedDataSet.GetXml(), actualDataSet.GetXml());

By comparing the XML serialised output of both DataSets we can ensure that the structure and data are identical.

Tags: DataSet, TDD, Unit testing