Question

When I have a Dictionary<string, int> actual and then create a completely new Dictionary<string, int> expected with the same values as actual.

• Calling Assert.That(actual, Is.EqualTo(expected)); makes the test pass.

• When using Assert.That(actual, Is.EquivalentTo(expected)); the test doesn’t pass.

What is the difference between EqualTo() and EquivalentTo()?

Edit:

The message of the exception when the test doesn’t pass is as follows:

Zoozle.Tests.Unit.PredictionTests.ReturnsDriversSelectedMoreThanOnceAndTheirPositions:
Expected: equivalent to < [Michael Schumacher, System.Collections.Generic.List`1[System.Int32]] >
But was:  < [Michael Schumacher, System.Collections.Generic.List`1[System.Int32]] >

My code looks like this:

[Test]
public void ReturnsDriversSelectedMoreThanOnceAndTheirPositions()
{
    //arrange
    Prediction prediction = new Prediction();

    Dictionary<string, List<int>> expected = new Dictionary<string, List<int>>()
    {
        { "Michael Schumacher", new List<int> { 1, 2 } }
    };

    //act
    var actual = prediction.CheckForDriversSelectedMoreThanOnce();

    //assert
    //Assert.That(actual, Is.EqualTo(expected));
    Assert.That(actual, Is.EquivalentTo(expected));
}

public Dictionary<string, List<int>> CheckForDriversSelectedMoreThanOnce()
{
    Dictionary<string, List<int>> expected = new Dictionary<string, List<int>>();
    expected.Add("Michael Schumacher", new List<int> { 1, 2 });

    return expected;
}

Answer 1

Both works for me:

var actual = new Dictionary<string, int> { { "1", 1 }, { "2", 2 } };
var expected = new Dictionary<string, int> { { "1", 1 }, { "2", 2 } };

Assert.That(actual, Is.EqualTo(expected)); // passed
Assert.That(actual, Is.EquivalentTo(expected)); // passed

---

• Is.EqualTo() inside NUnit, if both objects are ICollection, uses CollectionsEqual(x,y) which iterates both to find the difference. I guess it’s equal to Enumerable.SequenceEqual(x,y)

• Is.EquivalentTo does this immediate because support sequences only: EquivalentTo(IEnumerable)