How to Mock a readonly property whose value depends on another property of the Mock

(As indicated by the tags, I am using moq).

I have an interface like this:

interface ISource
  string Name { get; set; }
  int Id { get; set; }

interface IExample
  string Name { get; }
  ISource Source { get; set; }

In my application, concrete instances of IExample accept a DTO (IDataTransferObject) as the Source. Some properties on the concrete implementation of IExample are simply delegated to the Source. Like this...

class Example : IExample
  IDataTransferObject Source { get; set; }

  string Name { get { return _data.Name; } }

I would like to create a standalone mock of IExample (standalone meaning that I cannot use a captured variable because several instances of the IExample mock will be created in the course of a test) and setup the Mock such that IExample.Name returns the value of IExample.Source.Name. So, I would like to create a mock something like this:

var example = new Mock<IExample>();
example.SetupProperty(ex => ex.Source);
example.SetupGet(ex => ex.Name).Returns(what can I put here to return ex.Source.Name);

Essentially, I want to configure the mock to return, as the value of one property, the value of a property of a subobject of the mock.



You could probably use:

example.SetupGet(ex => ex.Name).Returns(() => example.Object.Source.Name);

The value to be returned will then be determined when the property is accessed, and will be taken from Name property of the mock's Source property.

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