C# - Asserting two objects are equal in unit tests

You've got two different Board instances, so your call to Assert.AreEqual will fail. Even if their entire contents appear to be the same, you're comparing references, not the underlying values.

You have to specify what makes two Board instances equal.

You can do it in your test:

Assert.AreEqual(expected.Rows.Count, actual.Rows.Count);
Assert.AreEqual(expected.Rows[0].Cells[0], actual.Rows[0].Cells[0]);

// Lots more tests of equality...

Or you can do it in your classes: (note I wrote this on-the-fly - you'll want to adjust this)

public class Board
{
    public List<Row> Rows = new List<Row>();

    public override bool Equals(object obj)
    {
        var board = obj as Board;

        if (board == null)
            return false;

        if (board.Rows.Count != Rows.Count)
            return false;

        return !board.Rows.Where((t, i) => !t.Equals(Rows[i])).Any();
    }

    public override int GetHashCode()
    {
        // determine what's appropriate to return here - a unique board id may be appropriate if available
    }
}

public class Row
{
    public List<int> Cells = new List<int>(); 

    public override bool Equals(object obj)
    {
        var row = obj as Row;

        if (row == null)
            return false;

        if (row.Cells.Count != Cells.Count)
            return false;

        if (row.Cells.Except(Cells).Any())
            return false;

        return true;
    }

    public override int GetHashCode()
    {
        // determine what's appropriate to return here - a unique row id may be appropriate if available
    }
}

I used to override getHasCode and equals, but I never liked it since I don't want to change my production code for the sake of unit testing. Also it's kind of pain.

Then I turned too reflection to compare objects which was less invasive...but that's kind of lot of work (lots of corner cases)

In the end I use:

http://www.nuget.org/packages/DeepEqual/ Works great.

Update, 6 years later:

I now use the more general library fluentassertions for .NET it does the same as above but with more features and a nice DSL, the specific replacement would be: https://fluentassertions.com/objectgraphs/

Also after some years of experience, I still not recommend the override route, I'd even consider it a bad practice. If you're not careful you could introduce performance issues when using some Collections like Dictionaries. Also when the time would come where you will have a real business case to overload these methods you'd be in trouble because you'd have this test code in there already. Production code and test code should be kept separated, test code should not rely on implementation details or hacks to achieve their goal, this make them hard to maintain and understand.

ExpectedObjects would help you to compare equality by property value. It supports:

1. simple object: expected.ToExpectedObject().ShouldEqual(actual);
2. collection: expected.ToExpectedObject().ShouldEqual(actual);
3. composized object: expected.ToExpectedObject().ShouldEqual(actual);
4. partial compare: expected object need design with anonymous type, and use expected.ToExpectedObject().ShouldMatch(actual)

I love ExpectedObjects because of I only need to invoke 2 API for assertion of comparing object equality:

1. ShouldEqual()
2. ShouldMatch() for partial comparing