According to http://www.nntp.perl.org/group/perl.qa/2009/03/msg12165.html it seems that nested test notation similar to this:
1..3
ok 1
1..3
ok 1
ok 2
ok 1
ok 2
ok 3
ok 4
1..4
ok 3 - some name
ok 2 - some name
ok 3
ok
would not be too difficult to support. But the official site linked from Wikipedia: Test Anything Protocol does not mention this as the way to go.
Is there any other notation suggested for nested tests? If not then can you add this one to the specification?