Show HN: I transformed my library into a Node and 100% coverage and Travis tutorial (opens in new tab)

I'd mention one exception: when you're doing something very complicated in a single function. For instance, I recently had to write an algorithm that involved partitioning integers into intervals, and the solution was a very non-intuitive dynamic programming algorithm. I devoted several paragraphs of documentation to the how's and why's, along with additional comments every couple lines. I found it really useful, especially when I had to go back and fix an odd off-by-one error that only occurred in certain cases. In those situations, variable names can only help so much.

Thing here is, it can replace any Blog/Book/Posts whatever about RSS Parsing with Nodejs And a line-by-line documented Code is in such a case a better solution for those who want learn by reading Code :-) Surely, it's worse in big Projects. But there I miss often a detailed documentation about the implementation. Look for example to the strlen() Std implementation for C/C++(it was the same with Magic Hexcodes and so on, right?)

Totally agree! But basically this is a tutorial.

Imagine a function that is something like:

  function X(Y, Z){
    if(Y){
      foo();
    }
    if(Z){
      bar();
    }
  }

If you have tests like:

  X(true, false);
  X(false, true);

Then your code coverage from the "line" point of view is 100%. Those two tests execute every line of code. However, the two states:

  X(true, true);
  X(false, false);

have not been tested, and if foo() and bar() both manipulate some global state, or otherwise have side effects, then the system could still break.

This is an issue with many code coverage tools. The lines themselves have been executed, but not necessarily all program states.

Say you have the following code:

if (foo) { setSomeState() }

At least with tools I'm familiar with, your coverage will be 100% if you have one test with 'foo = true'.

That means that you could have odd untested behavior if not executing 'setSomeState()' leaves something important unset.... but you'd have 100% coverage.

Of course in practice, 100% state coverage is really impossible to achieve.