Contents
What is the purpose of mock objects?
Using mock objects allows developers to focus their tests on the behavior of the system under test without worrying about its dependencies. For example, testing a complex algorithm based on multiple objects being in particular states can be clearly expressed using mock objects in place of real objects.
What happens when we mock a class?
A mock replaces that dependency. You set expectations on calls to the dependent object, set the exact return values it should give you to perform the test you want, and/or what exceptions to throw so that you can test your exception handling code. In this way you can test the unit in question easily.
How are identity and value objects passed in DDD?
Our customer has an identity and two value objects. All of this state is passed via the parameterized constructor. There is no default constructor. The properties are read-only. This makes it possible to do validation. We make sure that created customers are in a valid state and are kept in a valid state.
How are entities and value objects defined in code?
Check out his book on the subject. Two important building blocks when we talk about code are entities and value objects. An object fundamentally defined not by its attributes, but by a thread of continuity and identity. Lets use Customer as an example: if ( id == Guid. Empty) throw new Exception ( “Id is invalid” );
How are entities and value objects used in debugging?
One useful thing while debugging code that interacts with your entities is the DebuggerDisplay attribute. In the example with our customer we will display the email for quick identification. An object that describes some characteristic or attribute but carries no concept of identity.
When to use email as a string in DDD?
Apart from using the customer Id, the email can also be a way of identification. And wouldn’t it be convenient to sometimes just use a string when dealing with emails. In the example above, Email has implicit conversion operators from and to string. It can be very convenient to pass in email as a string to the customer constructor.