Hands-On Design Patterns with C# and .NET Core

Unit tests

With the changes to the InventoryContext class, we no longer have a convenient property for getting the only instance of the class. This means that InventoryContext.Instance will need to be replaced, and, as a first attempt, let's create a method to return a new instance of InventoryContext, and use GetInventoryContext() instead of InventoryContext.Instance:

private IInventoryContext GetInventoryContext(){    return new InventoryContext();}

As expected, the unit tests fail with an error message: The given key was not present in the dictionary:

As we saw in the previous chapter, this is because the InventoryContext list of books is ...