Test2 has a new and different problem!

$ perl -wle 'use Test2::Bundle::Extended; my $foo = undef; cmp_ok($foo, "ne", ""); done_testing'
# Seeded srand with seed '20160814' from local date.
Use of uninitialized value $got in string ne at (eval in cmp_ok) -e line 1.
not ok 1
# Failed test at -e line 1.
# +-----+----+-------+
# | GOT | OP | CHECK |
# +-----+----+-------+
# |     | ne |       |
# +-----+----+-------+
1..1

ok, the table should show so that needs to be fixed.

not sure if you were implying the warning was a bug, the warning should be there, and as expected it is warning from the caller. trying to 'eq' against undef is usually a mistake and the warning is good.

My thoughts after seeing this is the warning aught to be part of the test output so its clear what its attached to.

# Failed test at -e line 1.
# +-----+----+-------+ ---
# | GOT | OP | CHECK | NOTES
# +-----+----+-------+ ---
# |     | ne |       | uninitialized value $got
# +-----+----+-------+ ---

Or something.

Also in other cases where there's string overload, you'd probably want some sort of "no-overload" depiction of the terms for clarity. ( That is, showing both the stringified value in the comparison, and the sources of those stringified values for clarity )

The warning is fine. It's showing two blanks that doesn't help debug the problem. What I would expect to see is something like:

# Seeded srand with seed '20160814' from local date.
Use of uninitialized value $got in string ne at (eval in cmp_ok) -e line 1.
not ok 1
# Failed test at -e line 1.
# +---------+----+-------+
# | GOT     | OP | CHECK |
# +---------+----+-------+
# | <UNDEF> | ne | ''    |
# +---------+----+-------+
1..1

The most important part is to display the <UNDEF>. The display of whitespace should be discussed in another issue.

Anyhow, I don't think it's worth the hassle of fixing this in Test::More.

I thought that as well at first, but then I realised maybe that's not really optimal for this table.

Its optimal-ish for this case, but when you start getting into escaping, line feeds and UTF8 Characters, forcing it to be displayed in a dumper-esque format might be more trouble than its worth.

Another errant thought I had was to display a secondary table, and so horrible cases like:

cmp_ok( undef, 'ne', bless( %thing, "classname" )) where "classname" has string overloads would do:

# +-------+----+---------------------+
# | GOT   | OP | CHECK               |
# +-------+----+---------------------+
# |       | ne |                     |
# +-------+----+---------------------+
# | undef | ne | bless(...,classname)|
# +-------+----+---------------------+

Because clearly, neither the first row or the second row of this table is illuminating on its own.

I think empty strings, and strings that are only space characters (as in ascii space, not tabs, or other whitespace), should be quoted in the table. any other strings render sanely and I do not want to add quotes.

How are you going to differentiate between

$expected = q[''];

and

$expected = q[];

# +---------+----+-------+
# | GOT     | OP | CHECK |
# +---------+----+-------+
# | "''"    | eq | ""    |
# +---------+----+-------+

And before you ask.

# +---------+----+-------+
# | GOT     | OP | CHECK |
# +---------+----+-------+
# | "\"\""  | eq | ""    |
# +---------+----+-------+

We should move this discussion to Test-More/Test2-Suite#60

The test2 related bits of this should be moved to a ticket in Test2::Suite. This ticket only covers cmp_ok in Test::More.