Re: Do we need subtests in TAP?

[Michael G Schwern]

On 2011.10.29 1:51 AM, Adrian Howard wrote:
> On 29 Oct 2011, at 09:18, Michael G Schwern <schw...@pobox.com> wrote:
> [snip]
>> Do you find *blocks with their own name and plan* convenient, or subtests
>> which have their own separate test state (as currently implemented)
> 
> This may be me being dim - but I'm not really groking the distinction you're
> making. Could you give an example of the kind of difference that you're
proposing?

It's *mostly* internal, but here's an example to explain the difference.

Here's how subtests currently work:

    use Test::More;

    pass("First test");

    subtest 'An example subtest' => sub {
        plan tests => 2;

        pass("This is a subtest");
        pass("So is this");
    };

    pass("Third test");

    done_testing();
    __END__
    This would produce.

    ok 1 - First test
        1..2
        ok 1 - This is a subtest
        ok 2 - So is this
    ok 2 - An example subtest
    ok 3 - Third test
    1..3

As far as the state of the test is concerned, there's not a lot of difference
between

    subtest 'An example subtest' => sub {
        plan tests => 2;

        pass("This is a subtest");
        pass("So is this");
    };

and

    pass("An example subtest");

The subtest is one test.  Its internals have no more effect on the overall
test than any single test, whether it runs one or one hundred.

What I'm asking would it make much difference to how subtests are used if it
was like this:

    use Test::More;

    pass("First test");

    subtest 'An example subtest' => sub {
        plan tests => 2;

        pass("This is a subtest");
        pass("So is this");
    };

    pass("Last test");

    done_testing();
    __END__
    This would produce.

    ok 1 - First test
    # An example of a subtest
    ok 2 - This is a subtest
    ok 3 - So is this
    ok 4 - Last test
    1..4

Now the subtest is just a block with its own name and plan.  The plan is
internally enforced by Test::Builder, TB makes sure that two tests are run
inside the block.  Otherwise tests run inside a subtest are no different from
any other.

Another example is:

    subtest 'An example subtest' => sub {
        plan tests => 2;
        plan skip_all => "Because" if $something;

        pass("This is a subtest");
        pass("So is this");
    };

would become exactly equivalent to:

    SKIP: {
        skip "Because", 2 if $something;

        pass("This is a subtest");
        pass("So is this");
    }

It becomes just a better way of writing a skip block.

David already pointed out that if you're the sort of person who eyeballs TAP
(I do), the indentation is a nice visual distinction.  Anything else?


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