Given mkd;
# a

b

# c

d

Execute (]] same level):
  AssertEqual line('.'), 1
  normal ]]
  AssertEqual line('.'), 5
  normal [[
  AssertEqual line('.'), 1

Given mkd;
# a

b

## c

d

Execute (]] different levels level):
  AssertEqual line('.'), 1
  normal ]]
  AssertEqual line('.'), 5
  normal [[
  AssertEqual line('.'), 1

Given mkd;
# a

b

## c

d

# e

f

Execute (][ different levels level):
  AssertEqual line('.'), 1
  normal ][
  AssertEqual line('.'), 9
  normal []
  AssertEqual line('.'), 1

Given mkd;
# a

b

Execute (]c):
  normal! 3G
  AssertEqual line('.'), 3
  normal ]c
  AssertEqual line('.'), 1

Given mkd;
# a

Execute (Toc does not set nomodifiable on other files):
  " Sanity check.
  Assert &modifiable

  :Toc
  :lclose
  :edit a

  Assert &modifiable