Question

Considering such code:

class ToBeTested { public:   void doForEach() {     for (vector<Contained>::iterator it = m_contained.begin(); it != m_contained.end(); it++) {        doOnce(*it);        doTwice(*it);        doTwice(*it);     }   }   void doOnce(Contained & c) {     // do something   }   void doTwice(Contained & c) {     // do something   }    // other methods private:   vector<Contained> m_contained; } 

I want to test that if I fill vector with 3 values my functions will be called in proper order and quantity. For example my test can look something like this:

tobeTested.AddContained(one); tobeTested.AddContained(two); tobeTested.AddContained(three);  BEGIN_PROC_TEST() SHOULD_BE_CALLED(doOnce, 1) SHOULD_BE_CALLED(doTwice, 2) SHOULD_BE_CALLED(doOnce, 1) SHOULD_BE_CALLED(doTwice, 2) SHOULD_BE_CALLED(doOnce, 1) SHOULD_BE_CALLED(doTwice, 2)  tobeTested.doForEach() END_PROC_TEST() 

How do you recommend to test this? Are there any means to do this with CppUnit or GoogleTest frameworks? Maybe some other unit test framework allow to perform such tests?

I understand that probably this is impossible without calling any debug functions from these functions, but at least can it be done automatically in some test framework. I don’t like to scan trace logs and check their correctness.

UPD: I’m trying to check not only the state of an objects, but also the execution order to avoid performance issues on the earliest possible stage (and in general I want to know that my code is executed exactly as I expected).

Answer 1

If you’re interested in performance, I recommend that you write a test that measures performance.

Check the current time, run the method you’re concerned about, then check the time again. Assert that the total time taken is less than some value.

The problem with check that methods are called in a certain order is that your code is going to have to change, and you don’t want to have to update your tests when that happens. You should focus on testing the actual requirement instead of testing the implementation detail that meets that requirement.

That said, if you really want to test that your methods are called in a certain order, you’ll need to do the following:

1. Move them to another class, call it Collaborator
2. Add an instance of this other class to the ToBeTested class
3. Use a mocking framework to set the instance variable on ToBeTested to be a mock of the Collborator class
4. Call the method under test
5. Use your mocking framework to assert that the methods were called on your mock in the correct order.

I’m not a native cpp speaker so I can’t comment on which mocking framework you should use, but I see some other commenters have added their suggestions on this front.