单元测试-如何对对象进行快照？

Question

I'm writting my first unit tests in VS2012 using Moq.

I need to create an object that takes in multiple input parameters (not all are passed through interfaces).

I've minimized the code for the sake of the example. Here's what i'm trying to do:

  var mockLoopControl = new Mock<LoopControl>();
  var LoopEngine = new LoopEngine(mockLoopControl.Object);

The LoopControl object is complex, has a lot of members which are used in the LoopEngine constructor.

For example the LoopEngine constructor performs operations with loopControl.ContextData which is again an object with a lot of members.

From my understanding i need to assign data to the members that are used using Mock.Setup() . Is it possible to take for example a snapshot of the loopControl.ContextData object at application runtime and use it afterwards in my unit tests?

I can figure out how it's possible to write unit tests for such complex architectures.

I hope i made myself clear :) Thanks for helping out.

Dan

Answer 1

You mock it so you don't need to create that complex structure. If LoopEngine needs to use something from LoopControl maybe it is doing to much? Maybe it should delegate some of its work to LoopControl or other object? You should probably extract some other objects and do something else.

So it seems to me like you are trying to solve wrong problem here a little bit.

And if you want to test more functionality, you are likely doing integration testing. Then you may need to have more complex object structure - right. But you don't necessarily need to use mocks then, but rather checking results in real sittuations.

Answer 2

As far as I've understood your problem, you don't want to mock hundreds of properties of LoopControl , right? Looks like your unit-testing of LoopEngine is getting tricky because of tight coupling between LoopControl and LoopEngine . You have several options here

1. Stick on with mocking (I prefer to call it substitution, just not to mess with mock/fake/stub terminology).
2. Refactor LoopEngine class constructor to accept ILoopControl and LoopControl class to implement ILoopControl. It would ease mocking a lot.
3. Refactor LoopControl other ways, 'cause loopControl.ContextData doesn't sound good for me (possible mix of model and controller or smth like this). By reviewing your LoopControl class and it's aims you would probably extract some other class, that holds exactly what is needed for LoopEngine initialization (higher cohension is always a plus).
4. Don't bother with any refactoring and unit-testing and doing some integration testing of the LoopEngine and LoopControl pair (but any errors would require more investigation effort).

Answer 3

A common approach to handline unit tests in this way is to simply create a fake stand-in object that presents the class you are testing with the data you want it to be presented with in order to test it. Than you can isolate the class you are testing and test it using known values.

It should be relatively simple to write quick static classes that are "stand-in" for your test.