比较测试中的2个列表

Question

I am trying to make a test stub to check if the AddProduct method works or not.

I am getting a list of all the Products from the database

List<Product> ProductsBeforePlusNewProd = new ProductsBL().getAllProducts().ToList();

Populating the new product to add

 Product newProduct = new Product();
        newProduct.ProductName = ...

Adding the newProduct to the database

new ProductsBL().addProduct(newProduct);

Adding the same product to the list ProductsBeforePlusNewProd which will hold the previous products and the new one - (this is the expected result)

getting the whole list after adding the product to database

List<Product> ProductsAfter = new ProductsBL().getAllProducts().ToList();

Then this fails

CollectionAssert.AreEqual(ProductsBeforePlusNewProd, ProductsAfter);

What am I missing here ? This is my first test stub

EDIT : Error message : CollectionAssert.AreEqual failed. (Element at index 0 do not match.)

Answer 1

As pascx64 already showed, you can implement IEquatable at Product . But if you don't want to (or can't) change the implementation of Product , you could implement an IComparer :

    public class ProductComparer : IComparer
    {
        public int Compare(object x, object y)
        {
            // compare the two objects
        }
    }

You can than use

CollectionAssert.AreEqual(ProductsBeforePlusNewProd, ProductsAfter, new ProductComparer());

Answer 2

This will compare the list instances, not the items. I suggest you use IEnumerable.SequenceEquals (your item must implement equals)

Answer 3

Two collections are equal if they have the same elements in the same order and quantity. Elements are equal if their values are equal, not if they refer to the same object. The values of elements are compared using Equals by default. Are you sure that the elements in the both collections are equal? You need to implement IEquatable in Product class.

Answer 4

I think you need to implement IEquatable in your Product class :

public class Product : IEquatable
{
    public string ProductName;
    public bool Equals( object o )
    {
        Product other = o as Product;
        if( other == null ) 
             return false;
        return ProductName == other.ProductName;
    }
}

By default, the CollectionAssert.AreEquals will only check if the two references refer to the same object