Assert to compare two lists of objects C#

问题

I am currently trying to learn how to use unit testing, and I have created the actual list of 3 animal objects and the expected list of 3 animal objects. The question is how do I Assert to check the lists are equal? I have tried CollectionAssert.AreEqual and Assert.AreEqual but to no avail. Any help would be appreciated.

The test method:

  [TestMethod]
    public void createAnimalsTest2()
    {
        animalHandler animalHandler = new animalHandler();
        // arrange
        List<Animal> expected = new List<Animal>();
        Animal dog = new Dog("",0);
        Animal cat = new Cat("",0);
        Animal mouse = new Mouse("",0);
        expected.Add(dog);
        expected.Add(cat);
        expected.Add(mouse);
        //actual
        List<Animal> actual = animalHandler.createAnimals("","","",0,0,0);


        //assert
        //this is the line that does not evaluate as true
        Assert.Equals(expected ,actual);

    }

回答1:

Just incase someone comes across this in the future, the answer was I had to create an Override, IEqualityComparer as described below:

public class MyPersonEqualityComparer : IEqualityComparer<MyPerson>
{
public bool Equals(MyPerson x, MyPerson y)
{
    if (object.ReferenceEquals(x, y)) return true;

    if (object.ReferenceEquals(x, null)||object.ReferenceEquals(y, null)) return false;

    return x.Name == y.Name && x.Age == y.Age;
}

public int GetHashCode(MyPerson obj)
{
    if (object.ReferenceEquals(obj, null)) return 0;

    int hashCodeName = obj.Name == null ? 0 : obj.Name.GetHashCode();
    int hasCodeAge = obj.Age.GetHashCode();

    return hashCodeName ^ hasCodeAge;
}

}

回答2:

That is correct, as the lists are 2 different objects containing the similar data.

In order to get compare lists you should use the CollectionAssert

CollectionAssert.AreEqual(expected ,actual);

That should do the trick.

回答3:

I am of the opinion that implementing the IEqualityComparer (Equals() and GetHashCode()) for only testing purpose is a code smell. I would rather use the following assertion method, where you can freely define that on which properties you want to do the assertions:

public static void AssertListEquals<TE, TA>(Action<TE, TA> asserter, IEnumerable<TE> expected, IEnumerable<TA> actual)
{
    IList<TA> actualList = actual.ToList();
    IList<TE> expectedList = expected.ToList();

    Assert.True(
        actualList.Count == expectedList.Count,
        $"Lists have different sizes. Expected list: {expectedList.Count}, actual list: {actualList.Count}");

    for (var i = 0; i < expectedList.Count; i++)
    {
        try
        {
            asserter.Invoke(expectedList[i], actualList[i]);
        }
        catch (Exception e)
        {
            Assert.True(false, $"Assertion failed because: {e.Message}");
        }
    }
}

In action it would look like as follows:

    public void TestMethod()
    {
        //Arrange
        //...

        //Act
        //...

        //Assert
        AssertAnimals(expectedAnimals, actualAnimals);
    }

    private void AssertAnimals(IEnumerable<Animal> expectedAnimals, IEnumerable<Animal> actualAnimals)
    {
        ListAsserter.AssertListEquals(
            (e,a) => AssertAnimal(e,a),
            expectedAnimals,
            actualAnimals);
    }

    private void AssertAnimal(Animal expected, Animal actual)
    {
        Assert.Equal(expected.Name, actual.Name);
        Assert.Equal(expected.Weight, actual.Weight);
        //Additional properties to assert...
    }

I am using XUnit for the simple Assert.True(...) and Assert.Equals(), but you can use any other unit test library for that. Hope it helps someone! ;)

来源：https://stackoverflow.com/questions/19562505/assert-to-compare-two-lists-of-objects-c-sharp

标签

unit-testing

tdd

assert