Back to Basics: Testing in C++ - Phil Nash - CppCon 2023

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Back to Basics: Testing in C++ - Phil Nash - CppCon 2023
github.com/CppCon/CppCon2023
If we’re writing tests for our code we probably think we should write more - or write better tests. If we’re not already writing tests perhaps we think we should start. Or perhaps we are not, yet, convinced they are worth it?
This session will introduce you to the benefits of testing and how to get started and be effective.
We’ll look at:
* What does testing even mean?
* What types of testing are there, and what should I focus on?
* Should I use a test framework? If so which one?
* What are the testing best practices?
* What are some common challenges and pitfalls to overcome?
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Phil Nash
Phil is the original author of the C++ test framework, Catch2, and composable command line parser, Clara. As Developer Advocate at Sonar he's involved with SonarQube, SonarLint and SonarCloud, particularly in the context of C++. He's also a member of the ISO C++ standards committee, organiser of C++ London and C++ on Sea, as well as co-host and producer of CppCast. More generally he's an advocate for good testing practices, TDD and using the type system and functional techniques to reduce complexity and increase correctness. He's previously worked in Finance and Mobile offers training and coaching in C++ and TDD.
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[@steptoevs996]

I think the only reason some Developers do not write test, it is because of the overhead of installing dependencies of that or this Framework. C++ still annoying to manage dependencies.

[@kuhluhOG]

8:10 Personally I always find integration tests considerably harder to write (and more time consuming to write in total) than unit tests. I also consider integration tests in general more important than unit tests, because while most units you would unit test are small and simple enough that you can (mostly) make sure that they work by looking at it (and if it isn't, a unit test normally isn't that hard to write, even without a test framework), that doesn't hold for integration tests (let alone even system tests).

[@TheOnlyAndreySotnikov]

42:39 in my 30+ years of development experience I've never seen methods like size()/SIze()/length()... were responsible for any kind of bugs. Unfortunately, 90% of unit tests are that level useless.

[@organichand-pickedfree-ran1463]

Is it possible to test for compilation errors these days? Like proper SFINAE use etc. Last time I checked it was impossible to do negative tests for some compile-time things.

[@kingduckVI]

In short: No, it is not really possible. The closest you can get is testing if a concept (C++20) is false, which will test if a certain expression/statement is valid given certain types.

[@KX36]

45:30 I don't think "arrange, assert precondition, act, assert postcondition" is a bad thing, and I might argue it is a single logical assertion as long as the asserts are checking the same thing pre and post action. After all, you don't want to waste time debugging an action that failed its assert because the precondition is not what was expected.

[@not_ever]

That was the point of using sections though. You can clearly define the precondition so if it fails its easier to see at a glance from the test output that your precondition is the problem and when you/others are reading your tests the delimination between pre and post conditions is clear.

[@doBobro]

"Classical" unit tests are quite damaging for industry concept. Basically it forces you to write enormous amount of testing code and dance with "isolation". Forces you to rewrite enormous amount of code during refactorings (tests doesn't work as refactoring-aid tool) and internal details changes (fragile tests). It's hardly surprising developers don't like to write unit tests.

[@TheOnlyAndreySotnikov]

Also, most unit tests look like this: "auto sqrt(auto x) { return 2; } ASSERT_EQ(2, sqrt(4));" In 90% of companies, unit testing is a cargo cult.