" Tests toc window auto-fit to longest header, but without exceeding half screen.

Given markdown;
# chap 1

# chap 2

# chap 3

# chap 4

# chap 5

# chap 6

# chap 7

# chap 8

# chap 9

# chap 10

# chap 11

# chap 12

## chap 12.1

### chap 12.1.1

#### chap 12.1.1.1

##### chap 12.1.1.1.1

###### chap 12.1.1.1.1.1

# chap 13

Execute (toc window autofit width):
  set number
  let g:vim_markdown_toc_autofit = 1
  let line = '###### chap 12.1.1.1.1.1'
  AssertEqual getline('33'), line
  :Toc
  let real_width = winwidth(0)
  :lclose
  let expected_width = len(line) + 2*5 + 1 + 3 - 7
  AssertEqual real_width, expected_width
" 2 spaces * 5 additional header levels + 1 space for first header +
" 3 spaces for line numbers - 7 chars ('###### ') that don't show up on the TOC