CODEWITHSUNDEEP
unit-testingfakeiteasy
CJ_
CJ_

Reputation: 79

FakeItEasy - how to test virtual method

I am using FakeItEasy to fake class to do the following unit test. When I debug the unit test step by step, noticed that it will not step into original method -->IsOrderHasToBeCharged(). Instead, it always default the returned value as False. Is it because the method is marked as virtual in the working class? Is there any other way to do the unit test for that method?

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Upvotes: 4

Views: 1442

Answers (1)

Blair Conrad
Blair Conrad

Reputation: 242030

When I debug the unit test step by step, noticed that it will not step into original method -->IsOrderHasToBeCharged(). Instead, it always default the returned value as False. Is it because the method is marked as virtual in the working class?

Yes. This is exactly right. When FakeItEasy creates a fake, it intercepts all calls to virtual methods and provides its own implementation, as explained at Overrideable members are faked.

If you wanted to have the original IsOrderHasToBeCharged method to be called, you could configure the fake to call the base method. This can be done for the single method, like this:

A.CallTo(() => switchHandler.IsOrderHasToBeCharged(payCode, amount))
    .CallsBaseMethod();

or for every method on the fake, at creation time:

var switchHandler = A.Fake<ChargeProcessorSwitchHandler>(
     options => options.CallsBaseMethods());

Either of these will cause the original IsOrderHasToBeCharged to be called.

However, I'm compelled to note that this is probably not the best approach for this particular test. In general, faking the system under test is a bad idea, as it can introduce confusion, similar to what you've already seen. In general, isolation frameworks ("faking frameworks") should be used to fake the types that the system under test collaborates with. Then an actual system under test is instantiated in the test and exercised.

In this case, ChargeProcessorSwitchHandler has no collaborators, so I think you'd be better off replacing 

var switchHandler = A.Fake<ChargeProcessorSwitchHandler>();

with

var switchHandler = new ChargeProcessorSwitchHandler();

Then you can leave FakeItEasy out of the test altogether.

Upvotes: 6

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