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Sun, 25 Jan 2009

Test Suite Reorganization: How to move tests


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The Perl 6 test suite started its life in the Pugs Subversion repository, containing regression tests and one-to-one translations of the synopsis documents into tests.

If you check out the pugs repository via svn checkout http://svn.pugscode.org/pugs and go the newly created directory pugs, you can find all these tests in the directory t.

When it became clear that this test suite would grow into the official Perl 6 test suite, and would be shared by multiple implementations, it became clear that it needed some reorganization; many tests where specific to pugs, or didn't reflect the actual state of the synopsis.

So somebody created the directory t/spec/, and began to move the old tests there, reviewing them on the way if they still represent the current state of the Synopsis.

t/spec/ is what we call the "official Perl 6 test suite" nowadays, and all things in there should be covered by the specifications. It is organized in subdirectories which are all named in the scheme SXX-section, where XX stands for the number of a Synopsis, and section for a section in that synopsis. There is another dir called integration, in which tests live that can't be mapped to a single synopsis, or that are regression tests that are worth sharing with other implementations.

(The synopsis are located in docs/Perl6/Spec in the pugs repo, and are available as HTML at http://www.perlcabal.org/syn/">.

At the time of writing (2009-01-25) there are still more than 6000 tests in 155 in the non-official part of the pugs repository (not counting those under unspecced and pugs, which probably never will become part of the official suite) that need to be reviewed, and if still up-to-date, moved.

Reviewing and moving tests

The typical procedure looks like this:

First step, pick a test file in t/ (outside of spec, pugs, examples or unspecced). For the beginner builtins/ might be a good starting point, since you don't need to know a lot about the language to check if the test file is good.

As an example we look at blocks/nested_named.t, which in its current state looks like this:

use v6;

use Test;

=begin desc

Tests for nested subs in Apocalypse 6

=end desc 

plan 3;

sub factorial (Int $n) {
    my sub facti (Int $acc, Int $i) {
        return $acc if $i > $n;
        facti($acc * $i, $i + 1);
    }
    facti(1, 1);
} ;

is factorial(1), 1, "Checking semantics... 1";
is factorial(2), 2, "Checking semantics... 2";
is factorial(0), 1, "Checking semantics... 0";

# vim: ft=perl6

Let's look at what it does: It declares a sub one parameter $n, and then declares an inner sub, which uses the parameter of the outer sub. That's a closure, or at least something very similar. So it essentially tests signatures, and closures.

As the second step we have to find out where that behavior is specced.

$ cd ~/pugs/doc/Perl6/Spec
$ grep -ic closure S*.pod
S01-overview.pod:0
S02-bits.pod:16
S03-operators.pod:9
S04-control.pod:42
S05-regex.pod:33
S06-routines.pod:19
S07-iterators.pod:0
S09-data.pod:10
S10-packages.pod:0
S11-modules.pod:0
S12-objects.pod:23
S13-overloading.pod:0
S16-io.pod:0
S17-concurrency.pod:5
S19-commandline.pod:2
S22-package-format.pod:0
S26-documentation.pod:0
S29-functions.pod:4

So mostly S04, S05, S06 and S12 talk about closures. S05 is regexes - not our topic. S12 is Objects - not exactly what we're looking for either. S04 covers blocks and control structures (blocks are more interesting), and S06 covers subroutines, signatures and the like - bingo!

So looking through S04 we notice sentences like Every block is a closure and S06 contains examples of positional parameters that look very much like ours. Grep'ping through the synopsis for my sub we also find a few examples, so it looks like allowed syntax too. Let's decide it's indeed a good test (in case of doubt, ask in #perl6 on irc.freenode.org).

I usually move larger test files, while for smaller test files I look for existing test files (with similar topic, of course) in t/spec into which I can merge them. Since I didn't find one in this case I type

svn mv t/blocks/nested_named.t t/spec/S06-signatures/closure-over-parameters.t
svn ci -m '[t] moved nested_named.t to spec/' t/

Now the test is moved, and the change commit - success.

But wait, we can do more. The documentation in the file referred to the Apocalypses (which are mostly of historical interest), not the Synopsis - so let's change that. Also the test descriptions aren't very good, so let's find something more descriptive. Also we could add one more test of the same scheme as the existing ones, just to be sure.

The updated version looks like this:

use v6;

use Test;

=begin desc

Closure over parameters of outer subs, as per
# L<S04/The Relationship of Blocks and Declarations/"Every block is a
# closure">
# L<S06/Dynamically scoped subroutines>

=end desc 

plan 4;

sub factorial (Int $n) {
    my sub facti (Int $acc, Int $i) {
        return $acc if $i > $n;
        facti($acc * $i, $i + 1);
    }
    facti(1, 1);
} ;

is factorial(0), 1, "closing over params of outer subs (0)";
is factorial(1), 1, "closing over params of outer subs (1)";
is factorial(2), 2, "closing over params of outer subs (2)";
is factorial(3), 6, "closing over params of outer subs (3)";

# vim: ft=perl6

The weird things in the test descriptions are so-called smartlinks, described in the README.

Bonus points for the person who adds tests for the same thing, but with parameters that are passed by name.

According to the mantra "commit early, commit often", we type svn ci -m '[t/spec] cleaned up S06-signatures/closure-over-parameters.t a bit' t/spec/ and be happy.

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