Object Mentor Blog: Hello World Revisited

Hello World Revisited

Brett Schuchert — Thu, 20 May 2010 10:12:00 -0500

Surprising revelations while taking a TDD approach to writing hello world.

Here it nearly 21 years since I started writing in C++ (and more for C+) and I realize I’ve been blindly writing main functions to actually do something.

This insanity must stop!

What am I talking about? Read it here.

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Tue, 13 Jul 2010 16:59:36 -0500

This is a very helpful article. I was writing a new program from scratch (which I actually don’t do that often, I mostly maintain) and remembered this article. I did something slightly different in that I had (in C++)

int main( int argc, char* argv[] ) { return object->callFunction( argc, argv );

}

Not only did this make my entire program testable, but it really helped with the design of the program as well. Instead of writing a function that could only be used one time, I wrote a class that I could reuse for other programs if needed.

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"Hello World Revisited" by Brett Schuchert

Mon, 31 May 2010 11:11:02 -0500

Stan,

?? can you be a bit more specific? On what have I changed my mind?

As for \n versus std::endl, I agree. I should be consistent. I originally tried to do that, but since endl is an inserter, it’s not obvious how to extract its result into a value I can use. (Yes, build another stringstream, write to it to build an expected result, extract the result as a string, etc.) By the point I got to that, I had observed something much different than expected upon starting this little exercise. So I went for the shiny thing rather than that.

As for returning 0 or not, right now, given the tests, returning 0 is OK I suppose. If it’s not, then add a test that would force a need for a different return and then update the method. So I don’t see a problem there at all.

Two tests in one unit test? I don’t follow your question. Your response is 10 days after the post. I don’t keep context for that long. So I cannot guess your point. I see one assertion per unit test, so how do I have two tests in one unit test? I have one test fixture, two unit tests, each with a single assert. So what do you see that I do not see?

"Hello World Revisited" by Stan

Sun, 30 May 2010 12:25:14 -0500

Questions, questions, questions Hmm a little while ago when you posted the bowling kata (http://blog.objectmentor.com/articles/2009/10/27/c-bowling-kata-result )I commented: “I have not used this framework yet many other C++ frameworks and they all return a result of the tests do you not want this information returned from main?”

To which you replied:

“When I run the tests they either pass or fail. If they pass, I don’t need more information. If they fail, then I first need to know which tests failed. I would know that from execution and I would start there. So what are you looking for?”

Can I ask what changed your mind?

“Even so, I’m bothered by checking for ”\n” in one place and using std::endl in another. For now, I’ll leave that as an exercise to the reader to decide if that’s really a problem or not.”

”\n” and std::endl preform mostly the same magic of transforming the new line char into a platform specific end line, with std::endl having the added functionality of flushing the buffer. There is no problem using std::endl and checking for ”\n” here.

Why are you returning 0 from the mainImpl and when will it ever not return 0, why not instead return the status of the buffer? Why do you have two tests in one unit test? Checking the return which is never none zero and the buffer contents.

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"Hello World Revisited" by Brett L. Schuchert

Fri, 21 May 2010 10:10:35 -0500

Markus,

I assure you, all of my tests failed the first time. I did not show those steps, for sure. However, to play devils advocate, since I knew the implementation and was just vetting it via tdd, I’m OK with tests passing in those situations.

What happens if I’m using a published algorithm? If I can follow it and the pseudo code doesn’t make too many assumptions, then I can write fewer tests. If, on the other hand, it’s hard to follow or leaves a lot to the reader (I’m thinking the shunting yard algorithm), then raw tdd makes more sense to me.

"Hello World Revisited" by Jason Y

Fri, 21 May 2010 00:27:12 -0500

I guess all that to say, “Hello world” apps in new languages for, e.g., 3rd- and 4th-year college students should be functions driven by interactive consoles, unit testing frameworks, or other drivers; they should include no main function.

"Hello World Revisited" by Jason Y

Fri, 21 May 2010 00:25:39 -0500

This reminded me of my college days, when every program I submitted was required to have a main function. I have never written a main function for work in the 2.5 years I have been a professional developer. What I have learned on my own since then how to use existing drivers such as NUnit and ASP .NET. These always drive my code.

That said, I think it’s time college courses focus on using other drivers for apps. Whole courses should be completed without the use of a main function. main should be taught as “This is how these drivers work under-the-hood, and here’s how you can write it” instead of “This is the first thing you write with every application.”

"Hello World Revisited" by Markus Gaertner

Thu, 20 May 2010 15:16:35 -0500

Awwww, there’s no failing unit test in your first “Hello World” step! :)