commit https://github.com/vim/vim/commit/5f1032d2a55b9417a0a6fa225e35089c98a5a419 Author: Bram Moolenaar <Bram@vim.org> Date: Tue Jun 7 22:16:36 2016 +0200 patch 7.4.1906 Problem: Collapsing channel buffers and searching for NL does not work properly. (Xavier de Gary, Ramel Eshed) Solution: Do not assume the buffer contains a NUL or not. Change NUL bytes to NL to avoid the string is truncated.

Tests for writefile()

STARTTEST
:source small.vim
:%delete _
:let f = tempname()
:call writefile(["over","written"], f, "b")
:call writefile(["hello","world"], f, "b")
:call writefile(["!", "good"], f, "a")
:call writefile(["morning"], f, "ab")
:call writefile(["", "vimmers"], f, "ab")
:bwipeout!
:$put =readfile(f)
:1 delete _
:w! test.out
:call delete(f)
:qa!
ENDTEST