An alternative idea for having "non-boolean tests" directly in the source. What i don't like about it, is that it makes the source less readable : it becomes harder to search the interesting parts of the code.

I think you got the wrong end of the stick about this.

In the normal way of things, a module, Your::Thing.pm, looks like this:

package Your::Thing;

## The subroutines and stuff that implement your module

1; ## finish with a true value to satisfy require/use
[download]

And the tests live in a bunch of .t files.

The "alternative idea" is that Your::Thing.pm looks like this:

package Your::Thing;

## The subroutines and stuff that implement your module

return 1 if caller; ## return a true value and exit when loaded as a m
+odule
package main;

### Write tests that use Your::Thing here.

...
[download]

You use the module in the normal way via use or require, and it works exactly as with the 'usual way' above.

To run the tests, you type:

>perl \Perl\site\lib\Your::Thing.pm
[download]

And the code that comes after the return 1 if caller; statement gets run. It really is as simple as that.

And whilst the tests and code exist in the same file, the module code is above that line, and the tests are below it. There is no interleaving. Nothing is "less readable". Nothing is "harder to search" for.

Indeed, maintenance is greatly simplified by having the code and tests within the same file.

Try it. You'll never go back :)