better Range:highlight(..) handling

spec/buffer_spec.lua

@@ -1,5 +1,5 @@
 local Buffer = require 'tt.buffer'
-local withbuf = require '__tt_test_tools'
+local withbuf = loadfile './spec/withbuf.lua'()
 
 describe('Buffer', function()
   it('should replace all lines', function()

spec/pos_spec.lua

@@ -1,5 +1,5 @@
 local Pos = require 'tt.pos'
-local withbuf = require '__tt_test_tools'
+local withbuf = loadfile './spec/withbuf.lua'()
 
 describe('Pos', function()
   it('get a char from a given position', function()

spec/range_spec.lua

@@ -1,6 +1,6 @@
 local Range = require 'tt.range'
 local Pos = require 'tt.pos'
-local withbuf = require '__tt_test_tools'
+local withbuf = loadfile './spec/withbuf.lua'()
 
 describe('Range', function()
   it('get text in buffer', function()

spec/withbuf.lua

@@ -0,0 +1,10 @@
+local function withbuf(lines, f)
+  vim.opt_global.swapfile = false
+
+  vim.cmd.new()
+  vim.api.nvim_buf_set_lines(0, 0, -1, false, lines)
+  local ok, result = pcall(f)
+  vim.cmd.bdelete { bang = true }
+  if not ok then error(result) end
+end
+return withbuf