Why does this test method fail?

Question

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

The *default* on classes is always reference equality. The lack of any documentation to the contrary usually means the default still applies. — Marc Gravell, Feb 22 '11 at 08:31

Jackson Pope · Accepted Answer · 2011-02-22T14:01:47.037

19

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.

edited Feb 22 '11 at 14:01

answered Feb 22 '11 at 08:29

Jackson Pope

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score 13 · Answer 2 · answered Feb 22 '11 at 08:30

13

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]);
}

answered Feb 22 '11 at 08:30

Darin Dimitrov

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Thanks for your help. I accepted you answer because SequenceEqual(...) in the other answers is not supported by List<> generic collections. Your solutions works :-) – nabulke Feb 22 '11 at 11:59
1

@nabulke: It is if you're targetting the .Net 3.5 framework or above and you have `using System.Linq;` in your file. But you're right, Darin's answer will always work. – Jackson Pope Feb 22 '11 at 14:04

score 5 · Answer 3 · edited May 23 '17 at 12:29

5

I think that this is what your are looking for:

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

Check this question

edited May 23 '17 at 12:29

Community

1
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answered Feb 22 '11 at 08:35

Morvader

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score 2 · Answer 4 · edited Jul 07 '20 at 05:14

2

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.

edited Jul 07 '20 at 05:14

סטנלי גרונן

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answered Jul 07 '20 at 04:44

fermendezmx

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score 0 · Answer 5 · answered Nov 06 '22 at 00:17

CollectionAssert.AreEqual(expected, actual);
Assert.IsTrue(expected.SequenceEqual(actual));
Assert.IsTrue(expected.SequenceEqual(actual));

These options don't work for me.

Probably the only viable option. Had to use this:

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

Why does this test method fail?

5 Answers5