test 'a\nc\n\n\n\n' 'a\nb\n\n\n'

test 'a\nb\nc\n' 'a\nc\n'

test '' ''

test 'a\nb\nc' 'a\nb\nc'

test 'a\nb\nc\nd\n' 'a\nd\n'

test 'a\nb\nc\nd\n' 'a\nc\ne\n'

test 'a\nb\nc\n' 'a\nc\n'

test 'a\n' 'c\na\nb\n'

test 'a\n' ''

test 'a\n' 'b\nc\n'

test 'a\n' 'c\na\n'

test '' 'adjfkjdjksdhfksj'

test '' 'ab'

test '' 'abc'

test 'a' 'a'

test 'ab' 'ab'

test 'abc' 'abc'

test 'a\n' 'a\n'

test 'a\nb' 'a\nb'

showdiff(

  'x\n\nx\n\nx\n\nx\n\nz\n',

  'x\n\nx\n\ny\n\nx\n\nx\n\nz\n'):

 'x\n\nx\n\n'

 6 6 '' -> 'y\n\n'

 'x\n\nx\n\nz\n'

showdiff(

  'x\n\nx\n\nx\n\nx\n\nz\n',

  'x\n\nx\n\ny\n\nx\n\ny\n\nx\n\nz\n'):

 'x\n\nx\n\n'

 6 6 '' -> 'y\n\n'

 'x\n\n'

 9 9 '' -> 'y\n\n'

 'x\n\nz\n'

showdiff(

  'a\nb\nb\nb\nc\n.\nd\ne\n.\nf\n',

  'a\nb\nb\na\nb\nb\nb\nc\n.\nb\nc\n.\nd\ne\nf\n'):

 0 0 '' -> 'a\nb\nb\n'

 'a\nb\nb\nb\nc\n.\n'

 12 12 '' -> 'b\nc\n.\n'

 'd\ne\n'

 16 18 '.\n' -> ''

 'f\n'

done

done

Nice diff for a trivial change:

showdiff(

  '<0\n-\n<1\n-\n<2\n-\n<3\n-\n<4\n-\n',

  '>0\n-\n>1\n-\n>2\n-\n>3\n-\n>4\n-\n'):

 0 3 '<0\n' -> '>0\n'

 '-\n'

 5 8 '<1\n' -> '>1\n'

 '-\n'

 10 13 '<2\n' -> '>2\n'

 '-\n'

 15 18 '<3\n' -> '>3\n'

 '-\n'

 20 23 '<4\n' -> '>4\n'

 '-\n'

showdiff(

  'a\n',

  'a\na\na\n'):

 'a\n'

showdiff(

  'a\n',

  'a\na\na\na\na\n'):

 'a\n'

Diff 3 to 1 lines - preference for balanced recursion:

showdiff(

  'a\na\na\n',

  'a\n'):

 0 2 'a\n' -> ''

 'a\n'

 4 6 'a\n' -> ''

Diff 5 to 1 lines - preference for balanced recursion:

showdiff(

  'a\na\na\na\na\n',

  'a\n'):

 0 4 'a\na\n' -> ''

 'a\n'

 6 10 'a\na\n' -> ''