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unit-testingargumentsrhino-mocks

RhinoMocks - Getting the value passed into an Indexer (this[])

I need to find out the value passed into an indexer.

My code (c#) that I need to test is as follows:

string cacheKey = GetCacheKey(cacheKeyRequest);
string cachedValue = myCache[cacheKey] as string;

So, I need to be able to identify the value of the "cacheKey" that was passed into the indexer.

I have attempted this using a Mock of the cache object:

var cache = MockRepository.GenerateMock<WebDataCache>();

The idea being that after the code had executed, I would query the mock to identify the value that had been passed into the indexer:

var actualCacheKey = cache.GetArgumentsForCallsMadeOn(a => a["somevalue"], opt => opt.IgnoreArguments())[0][0].ToString();

This gives me a compilation error: Only assignment, call, increment, decrement, and new object expressions can be used as a statement.

I saw one suggestion to make this a function in the following way: 

var actualCacheKey = cache.GetArgumentsForCallsMadeOn(a => a["somevalue"] = null, opt => opt.IgnoreArguments())[0][0].ToString();

This now compiles,but throws a run-time InvalidOperationException: No expectations were setup to be verified, ensure that the method call in the action is a virtual (C#) / overridable (VB.Net) method call.

Any suggestions? [Am using RhinoMocks.3.6.1]

Many thanks in advance

Griff

PS - I have previously posted this in http://groups.google.com/group/rhinomocks but after several days the view-count remains depressingly low.

Solution

  • The exception tells you exactly what is happening:

    InvalidOperationException: No expectations were setup to be verified, ensure that the method call in the action is a virtual (C#) / overridable (VB.Net) method call.

    Which means, in order for Rhino to properly work (or, in order for Castle to generate working proxies) your indexer has to be virtual. If you can't make it so, Rhino won't help you in this situation.

    Once you make your indexer virtual, it is simple task:

    var cache = MockRepository.GenerateMock<WebDataChache>();
cache.Expect(c => c["SomeKey"]).Returns("SomeValue");

// perform actual test

cache.VerifyAllExpectations();

    This ensures that cache is accessed with ["SomeKey"]. If key value will be different, test will fail at VerifyAllExpectations line.