Before you decide where your going to put your tests, what in this sample are you going to test?

• main()

  Can perl invoke a function and assign the values it returns to an array?

  Can it then pass a reference to that array to another function?

  Someone will say that you should test what happens if the first function returns no files. There are two ways to handle that.

  • If there are no files, there is nothing to do and the second function can simply do nothing if there is nothing to do.

    sub extract_file {
        my( $file_ref ) = @_;
        while( @$file_ref ) {
            my $file = shift @$fileref;
            ## Do stuff
        }
        return;
    }
    [download]

    Note: while not for because the latter will expand the array to a list within the sub, and you've pretty much negated any reason for passing a reference.

  • Alternatively, main could report the absence of files

    my @files = get_xml_files() or die "No XML files to process";
    [download]

    Do we need to test that?

    We might run a quick check using the debugger or a repl to ensure that the precedence works. But do we need to re-run that test every time? Is it likely to change?

• get_xml_files()

  We could critique this in the basis that it returns a list instead of an array reference.

  We could critique it on the basis that substituting a user defined sub for a single call to a built-in is unnecessary.

  But is there anything to test here?

• extract_file()

  Assigning a ref to an array of files, to a scalar called $file could be mildly confusing, but until we see how it is used, it's just nit-picking.

  Beyond that, the sub is empty. Can we really apply any tests until we can know what it is going to do?

I appreciate that the snippet is intended to promote replies about how to go about testing a stand alone script, not how to test this particular example. But in the absence of any real code, it is pretty much impossible to suggest good ways of testing.