Question

I have a .NET application with a web front-end, WCF Windows service back-end. The application is fairly simple – it takes some user input, sending it to the service. The service does this – takes the input (Excel spreadsheet), extracts the data items, checks SQL DB to make sure the items are not already existing – if they do not exist, we make a real-time request to a third party data vendor and retrieve the results, inserting them into the database. It does some logging along the way.

I have a Job class with a single public ctor and public Run() method. The ctor takes all the params, and the Run() method does all of the above logic. Each logical piece of functionality is split into a separate class – IParser does file parsing, IConnection does the interaction with the data vendor, IDataAccess does the data access, etc. The Job class has private instances of these interfaces, and uses DI to construct the actual implementations by default, but allows the class user to inject any interface.

In the real code, I use the default ctor. In my unit tests for the Run() method, I use all mock objects creating via NMock2.0. This Run() method is essentially the ‘top level’ function of this application.

Now here’s my issue / question: the unit tests for this Run() method are crazy. I have three mock objects I’m sending into the ctor, and each mock object sets expectations on themselves. At the end I verify. I have a few different flows that the Run method can take, each flow having its own test – it could find everything is already in the database and not make a request to vendor… or an exception could be thrown and the job status could be set to ‘failed’… OR we can have the case where we didn’t have the data and needed to make the vendor request (so all those function calls would need to be made).

Now – before you yell at me and say ‘your Run() method is too complicated!’ – this Run method is only a mere 50 lines of code! (It does make calls to some private function; but the entire class is only 160 lines). Since all the ‘real’ logic is being done in the interfaces that are declared on this class. however, the biggest unit test on this function is 80 lines of code, with 13 calls to Expect.BLAH().. _

This makes re-factoring a huge pain. If I want to change this Run() method around, I have to go edit my three unit tests and add/remove/update Expect() calls. When I need to refactor, I end up spending more time creating my mock calls than I did actually writing the new code. And doing real TDD on this function makes it even more difficult if not impossible. It’s making me think that it’s not even worth unit testing this top level function at all, since really this class isn’t doing much logic, it’s just passing around data to its composite objects (which are all fully unit tested and don’t require mocking).

So – should I even bother testing this high level function? And what am I gaining by doing this? Or am I completely misusing mock/stub objects here? Perhaps I should scrap the unit tests on this class, and instead just make an automated integration test, which uses the real implementations of the objects and Asserts() against SQL Queries to make sure the right end-state data exists? What am I missing here?

EDIT: Here’s the code – the first function is the actual Run() method – then my five tests which test all five possible code paths. I changed it some for NDA reasons but the general concept is still there. Anything you see wrong with how I’m testing this function, any suggestions on what to change to make it better? Thanks.

Answer 1

I guess my advice echos most of what is posted here.

It sounds as if your Run method needs to be broken down more. If its design is forcing you into tests that are more complicated than it is, something is wrong. Remember this is TDD we’re talking about, so your tests should dictate the design of your routine. If that means testing private functions, so be it. No technological philosophy or methodology should be so rigid that you can’t do what feels right.

Additionally, I agree with some of the other posters, that your tests should be broken down into smaller segments. Ask yourself this, if you were going to be writting this app for the first time and your Run function didn’t yet exist, what would your tests look like? That response is probably not what you have currently (otherwise you wouldn’t be asking the question). 🙂

The one benefit you do have is that there isn’t a lot of code in the class, so refactoring it shouldn’t be very painful.

EDIT

Just saw you posted the code and had some thoughts (no particular order).

1. Way too much code (IMO) inside your SyncLock block. The general rule is to keep the code to a minimal inside a SyncLock. Does it ALL have to be locked?
2. Start breaking code out into functions that can be tested independently. Example: The ForLoop that removes ID’s from the List(String) if they exist in the DB. Some might argue that the m_dao.BeginJob call should be in some sort of GetID function that can be tested.
3. Can any of the m_dao procedures be turned into functions that can tested on their own? I would assume that the m_dao class has it’s own tests somewhere, but by looking at the code it appears that that might not be the case. They should, along with the functionality in the m_Parser class. That will relieve some of the burden of the Run tests.

If this were my code, my goal would be to get the code to a place where all the individual procedure calls inside Run are tested on their own and that the Run tests just test the final out come. Given input A, B, C: expect outcome X. Give input E, F, G: expect Y. The detail of how Run gets to X or Y is already tested in the other procedures’ tests.

These were just my intial thoughts. I’m sure there are a bunch of different approaches one could take.