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I know how I would do it in python. This is built into the stdlibs testing library, with mocks. Maybe dependency injection and function pointers for the copy i

by tayo42 9mo ago

I know how I would do it in python. This is built into the stdlibs testing library, with mocks. Maybe dependency injection and function pointers for the copy if function. Then you can check the call counts in your tests. But idk the cpp eco system and what's available there to do it.

shagie 9mo ago
The python code would be def some_call(): return [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] def print_evens(nums): for n in filter(lambda n: n % 2 == 0, nums): print(n) def func(): filtered = list(filter(lambda n: n % 2 == 0, some_call())) print_evens(filtered) if __name__ == "__main__": func() How would you write a failing test that prevents the list from some_call() from having the same filter applied to it twice?
- tayo42 9mo ago
  You would use something like this https://docs.python.org/3/library/unittest.mock.html#unittest.mock.Mock.assert_called_once_with https://docs.python.org/3/library/unittest.mock.html#unittes... Then you would make the mock filter with patch and test the `func` function psuedo python code would be @patch(builtins.filter) def test_func_filter_calls(mock_filter): mock_filter.return_value = [2,4,6] func() mock_filter.assert_called_once_with([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
  - shagie 9mo ago
    That wouldn't fail though. It was called only once with [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. The second time it was called with [2, 4, 6, 8, 10]. Likewise, if some_call returned [2, 4, 6, 8, 10] instead, it should only be called with [2, 4, 6, 8, 10] once then. However, the purpose of this test then becomes questionable. Why are you testing implementation details rather than observable? Is there anything that you could observe that depended on the filter being called once or twice with the same filter function?
    - tayo42 9mo ago
      Did you try it? If it doesn't work there's also called once if you scroll up on the doc And as far as whether it's a good idea or not, I generally wouldn't, but was saying when it is important then you do have these tools available,llms aren't the first thing to check for these mistakes. It's up to the engineer to choose between trade offs for your scenario.
      - shagie 9mo ago
        Yes. The test passes. https://imgur.com/a/4qlTKlc https://imgur.com/a/4qlTKlc To try to monkey patch this in, you would need to also assert that it wasn't called with [2, 4, 6, 8, 10]. At which point, I would again ask "why are you testing that it _wasn't_ called with a given set of values?" The comment at the root of this is "Unit tests catch that kind of stuff". ... But unit tests aren't for testing internals of implementation but rather observable aspects of a function. Consider if the code was written so that it was def print_evens(nums): for n in nums: if n % 2 == 0: print(n) instead (with the filter being used in func()) This isn't something that unit tests can (or should) identify. It would come out in a code review that there is redundant functionality in func and print_evens. Using ChatGPT or another tool to assist in doing code reviews can be helpful (my original premise). https://chatgpt.com/share/697a64a6-33c0-8011-a0f8-ca4fec74ab1f https://chatgpt.com/share/697a64a6-33c0-8011-a0f8-ca4fec74ab... ChatGPT properly identifies the duplicated functionality (even though the code is using different idioms for doing the filtering for even numbers).
        tayo42 9mo ago
        The test pass because your patching print_even so the 2nd filter is never called. Which I guess, idk maybe think through the testing more and your code more before jumping to conclusions about how things are? Testing is one tool you have, and it can test the internal like this. Obviously there's a use for it if its in the Python stdlib This is in mockito https://stackoverflow.com/questions/39452438/mockito-how-to-verify-a-method-was-called-only-once-with-exact-parameters-ignor https://stackoverflow.com/questions/39452438/mockito-how-to-... this is in google testing library for cpp https://google.github.io/googletest/gmock_for_dummies.html https://google.github.io/googletest/gmock_for_dummies.html > Specify your expectations on them (How many times will a method be called? With what arguments? What should it do? etc.). If you never heard of this, I guess you learned something new? Im not a tutor though. I would read the docs more and experiment. Maybe chatgpt can help you with how tests can be written.

by tayo42 9mo ago

shagie 9mo ago

The python code would be def some_call(): return [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] def print_evens(nums): for n in filter(lambda n: n % 2 == 0, nums): print(n) def func(): filtered = list(filter(lambda n: n % 2 == 0, some_call())) print_evens(filtered) if __name__ == "__main__": func() How would you write a failing test that prevents the list from some_call() from having the same filter applied to it twice?

tayo42 9mo ago
You would use something like this https://docs.python.org/3/library/unittest.mock.html#unittest.mock.Mock.assert_called_once_with https://docs.python.org/3/library/unittest.mock.html#unittes... Then you would make the mock filter with patch and test the `func` function psuedo python code would be @patch(builtins.filter) def test_func_filter_calls(mock_filter): mock_filter.return_value = [2,4,6] func() mock_filter.assert_called_once_with([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
- shagie 9mo ago
  That wouldn't fail though. It was called only once with [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. The second time it was called with [2, 4, 6, 8, 10]. Likewise, if some_call returned [2, 4, 6, 8, 10] instead, it should only be called with [2, 4, 6, 8, 10] once then. However, the purpose of this test then becomes questionable. Why are you testing implementation details rather than observable? Is there anything that you could observe that depended on the filter being called once or twice with the same filter function?
  - tayo42 9mo ago
    Did you try it? If it doesn't work there's also called once if you scroll up on the doc And as far as whether it's a good idea or not, I generally wouldn't, but was saying when it is important then you do have these tools available,llms aren't the first thing to check for these mistakes. It's up to the engineer to choose between trade offs for your scenario.
    - shagie 9mo ago
      Yes. The test passes. https://imgur.com/a/4qlTKlc https://imgur.com/a/4qlTKlc To try to monkey patch this in, you would need to also assert that it wasn't called with [2, 4, 6, 8, 10]. At which point, I would again ask "why are you testing that it _wasn't_ called with a given set of values?" The comment at the root of this is "Unit tests catch that kind of stuff". ... But unit tests aren't for testing internals of implementation but rather observable aspects of a function. Consider if the code was written so that it was def print_evens(nums): for n in nums: if n % 2 == 0: print(n) instead (with the filter being used in func()) This isn't something that unit tests can (or should) identify. It would come out in a code review that there is redundant functionality in func and print_evens. Using ChatGPT or another tool to assist in doing code reviews can be helpful (my original premise). https://chatgpt.com/share/697a64a6-33c0-8011-a0f8-ca4fec74ab1f https://chatgpt.com/share/697a64a6-33c0-8011-a0f8-ca4fec74ab... ChatGPT properly identifies the duplicated functionality (even though the code is using different idioms for doing the filtering for even numbers).
      - tayo42 9mo ago
        The test pass because your patching print_even so the 2nd filter is never called. Which I guess, idk maybe think through the testing more and your code more before jumping to conclusions about how things are? Testing is one tool you have, and it can test the internal like this. Obviously there's a use for it if its in the Python stdlib This is in mockito https://stackoverflow.com/questions/39452438/mockito-how-to-verify-a-method-was-called-only-once-with-exact-parameters-ignor https://stackoverflow.com/questions/39452438/mockito-how-to-... this is in google testing library for cpp https://google.github.io/googletest/gmock_for_dummies.html https://google.github.io/googletest/gmock_for_dummies.html > Specify your expectations on them (How many times will a method be called? With what arguments? What should it do? etc.). If you never heard of this, I guess you learned something new? Im not a tutor though. I would read the docs more and experiment. Maybe chatgpt can help you with how tests can be written.