Why does this test method fail?

10
votes

Here's my test function (c#, visual studio 2010):

[TestMethod()]
public void TestGetRelevantWeeks()
{
List<sbyte> expected = new List<sbyte>() { 2, 1, 52, 51, 50, 49, 48, 47, 46, 45 };
List<sbyte> actual = new List<sbyte>() { 2, 1, 52, 51, 50, 49, 48, 47, 46, 45 };
Assert.AreEqual<List<sbyte>>(expected, actual);
}

Exception: Failed TestGetRelevantWeek Assert.AreEqual failed.
Expected:System.Collections.Generic.List 1[System.SByte].
Actual:System.Collections.Generic.List 1[System.SByte].

Does AreEqual only check equality of the reference, not the contents?

But then, the exception message would be confusing. I also couldn't find a documentation of the default equality comparer for a generic list.

Could you help to clarify why the test fails and what would be solutions for testing the equality of the contents of both lists?

Kind regards

4
c#visual-studio-2010unit-testing
The default on classes is always reference equality. The lack of any documentation to the contrary usually means the default still applies. - Marc Gravell

4 Answers

15
votes

The Assert.AreEqual() method does a reference equality test as you expected.

Assuming you're using .Net 3.5 or above, you can do this:

using System.Linq;

Assert.IsTrue(expected.SequenceEqual(actual));

Edit: Clarified when this option is available.

13
votes

Does AreEqual only check equality of the reference, not the contents?

Yeap.

To test the contents you could:

Assert.AreEqual(expected.Count, actual.Count);
for (var i = 0; i < expected.Count; i++)
{
    Assert.AreEqual(expected[i], actual[i]);
}
4
votes

I think that this is what your are looking for:

Assert.IsTrue(expected.SequenceEqual(actual));

Check this question

1
votes

You can also use CollectionAssert instead of Assert:

CollectionAssert.AreEqual(expected, actual);

I think it is much more simple and fancier than a loop over the collection of your test cases.