" Tests for expressions.

func Test_strgetchar()
  call assert_equal(char2nr('a'), strgetchar('axb', 0))
  call assert_equal(char2nr('x'), strgetchar('axb', 1))
  call assert_equal(char2nr('b'), strgetchar('axb', 2))

  call assert_equal(-1, strgetchar('axb', -1))
  call assert_equal(-1, strgetchar('axb', 3))
  call assert_equal(-1, strgetchar('', 0))
endfunc

func Test_strcharpart()
  call assert_equal('a', strcharpart('axb', 0, 1))
  call assert_equal('x', strcharpart('axb', 1, 1))
  call assert_equal('b', strcharpart('axb', 2, 1))
  call assert_equal('xb', strcharpart('axb', 1))

  call assert_equal('', strcharpart('axb', 1, 0))
  call assert_equal('', strcharpart('axb', 1, -1))
  call assert_equal('', strcharpart('axb', -1, 1))
  call assert_equal('', strcharpart('axb', -2, 2))

  call assert_equal('a', strcharpart('axb', -1, 2))
endfunc