diff --git a/test/unit/buffer_spec.lua b/test/unit/buffer_spec.lua
index 05fba684d6..a2e7bd91af 100644
--- a/test/unit/buffer_spec.lua
+++ b/test/unit/buffer_spec.lua
@@ -5,13 +5,10 @@ local helpers = require("test.unit.helpers")
 local to_cstr = helpers.to_cstr
 local eq      = helpers.eq
 local neq     = helpers.neq
+local NULL    = helpers.NULL
 
 local globals = helpers.cimport("./src/nvim/globals.h")
 local buffer = helpers.cimport("./src/nvim/buffer.h")
-local fileio = helpers.cimport("./src/nvim/fileio.h")
-local ex_docmd = helpers.cimport("./src/nvim/ex_docmd.h")
-local window = helpers.cimport("./src/nvim/window.h")
-local option = helpers.cimport("./src/nvim/option.h")
 
 describe('buffer functions', function()
 
@@ -215,7 +212,7 @@ describe('buffer functions', function()
 
   describe('build_stl_str_hl', function()
 
-    output_buffer = to_cstr(string.rep(" ", 100))
+    local output_buffer = to_cstr(string.rep(" ", 100))
 
     local build_stl_str_hl = function(pat)
       return buffer.build_stl_str_hl(globals.curwin,
diff --git a/test/unit/fileio_spec.lua b/test/unit/fileio_spec.lua
index 180fc3c184..3e3c36617d 100644
--- a/test/unit/fileio_spec.lua
+++ b/test/unit/fileio_spec.lua
@@ -4,6 +4,7 @@ local helpers = require("test.unit.helpers")
 local eq      = helpers.eq
 local ffi     = helpers.ffi
 local to_cstr = helpers.to_cstr
+local NULL    = helpers.NULL
 
 local fileio = helpers.cimport("./src/nvim/fileio.h")
 
diff --git a/test/unit/formatc.lua b/test/unit/formatc.lua
index f9397eaec6..3f86c5f1b1 100644
--- a/test/unit/formatc.lua
+++ b/test/unit/formatc.lua
@@ -124,13 +124,13 @@ end
 
 local function set(t)
   local s = {}
-  for i, v in ipairs(t) do
+  for _, v in ipairs(t) do
     s[v] = true
   end
   return s
 end
 
-local C_keywords = set {
+local C_keywords = set {  -- luacheck: ignore
   "break", "case", "char", "const", "continue", "default", "do", "double",
   "else", "enum", "extern", "float", "for", "goto", "if", "int", "long",
   "register", "return", "short", "signed", "sizeof", "static", "struct",
@@ -154,13 +154,13 @@ local C_keywords = set {
 --  The first one will have a lot of false positives (the line '{' for
 --  example), the second one is more unique.
 local function formatc(str)
-  local tokens = TokeniseC(str)
+  local toks = TokeniseC(str)
   local result = {}
   local block_level = 0
   local allow_one_nl = false
   local end_at_brace = false
 
-  for i, token in ipairs(tokens) do
+  for _, token in ipairs(toks) do
     local typ = token[2]
     if typ == '{' then
       block_level = block_level + 1
@@ -213,8 +213,8 @@ local function formatc(str)
 end
 
 -- standalone operation (very handy for debugging)
-local function standalone(...)
-  Preprocess = require("preprocess")
+local function standalone(...)  -- luacheck: ignore
+  local Preprocess = require("preprocess")
   Preprocess.add_to_include_path('./../../src')
   Preprocess.add_to_include_path('./../../build/include')
   Preprocess.add_to_include_path('./../../.deps/usr/include')
diff --git a/test/unit/garray_spec.lua b/test/unit/garray_spec.lua
index e779cab8a7..9694e3c427 100644
--- a/test/unit/garray_spec.lua
+++ b/test/unit/garray_spec.lua
@@ -5,8 +5,6 @@ local internalize = helpers.internalize
 local eq = helpers.eq
 local neq = helpers.neq
 local ffi = helpers.ffi
-local lib = helpers.lib
-local cstr = helpers.cstr
 local to_cstr = helpers.to_cstr
 local NULL = helpers.NULL
 
@@ -48,7 +46,7 @@ local ga_size = function(garr)
   return ga_len(garr) * ga_itemsize(garr)
 end
 
-local ga_maxsize = function(garr)
+local ga_maxsize = function(garr)  -- luacheck: ignore
   return ga_maxlen(garr) * ga_itemsize(garr)
 end
 
@@ -65,8 +63,8 @@ local ga_data_as_ints = function(garr)
 end
 
 -- garray manipulation
-local ga_init = function(garr, itemsize, growsize)
-  return garray.ga_init(garr, itemsize, growsize)
+local ga_init = function(garr, itemsize_, growsize_)
+  return garray.ga_init(garr, itemsize_, growsize_)
 end
 
 local ga_clear = function(garr)
@@ -113,7 +111,7 @@ local ga_set_len = function(garr, len)
 end
 
 local ga_inc_len = function(garr, by)
-  return ga_set_len(garr, ga_len(garr) + 1)
+  return ga_set_len(garr, ga_len(garr) + by)
 end
 
 -- custom append functions
@@ -197,10 +195,9 @@ describe('garray', function()
   end)
 
   describe('ga_grow', function()
-    local new_and_grow
-    function new_and_grow(itemsize, growsize, req)
+    local function new_and_grow(itemsize_, growsize_, req)
       local garr = new_garray()
-      ga_init(garr, itemsize, growsize)
+      ga_init(garr, itemsize_, growsize_)
       eq(0, ga_size(garr))         -- should be 0 at first     
       eq(NULL, ga_data(garr))      -- should be NULL           
       ga_grow(garr, req)           -- add space for `req` items
@@ -306,7 +303,7 @@ describe('garray', function()
       ga_init(garr, ffi.sizeof("char"), 1)
       local str = "ohwell●●"
       local loop = 5
-      for i = 1, loop do
+      for _ = 1, loop do
         ga_concat(garr, str)
       end
 
@@ -321,7 +318,7 @@ describe('garray', function()
     end)
   end)
 
-  function test_concat_fn(input, fn, sep)
+  local function test_concat_fn(input, fn, sep)
     local garr = new_string_garray()
     ga_append_strings(garr, unpack(input))
     if sep == nil then
diff --git a/test/unit/helpers.lua b/test/unit/helpers.lua
index 5bcc661226..7b43b2218c 100644
--- a/test/unit/helpers.lua
+++ b/test/unit/helpers.lua
@@ -18,17 +18,9 @@ local function trim(s)
 end
 
 -- a Set that keeps around the lines we've already seen
-if cdefs == nil then
-  cdefs = Set:new()
-end
-
-if imported == nil then
-  imported = Set:new()
-end
-
-if pragma_pack_id == nil then
-  pragma_pack_id = 1
-end
+local cdefs = Set:new()
+local imported = Set:new()
+local pragma_pack_id = 1
 
 -- some things are just too complex for the LuaJIT C parser to digest. We
 -- usually don't need them anyway.
@@ -67,7 +59,7 @@ local function cimport(...)
   end
 
   local body = nil
-  for i=1, 10 do
+  for _ = 1, 10 do
     local stream = Preprocess.preprocess_stream(unpack(paths))
     body = stream:read("*a")
     stream:close()
diff --git a/test/unit/os/env_spec.lua b/test/unit/os/env_spec.lua
index 8e18c599d9..e0e12a24f2 100644
--- a/test/unit/os/env_spec.lua
+++ b/test/unit/os/env_spec.lua
@@ -1,11 +1,9 @@
 local helpers = require('test.unit.helpers')
 
 local cimport = helpers.cimport
-local internalize = helpers.internalize
 local eq = helpers.eq
 local neq = helpers.neq
 local ffi = helpers.ffi
-local lib = helpers.lib
 local cstr = helpers.cstr
 local to_cstr = helpers.to_cstr
 local NULL = helpers.NULL
@@ -15,15 +13,15 @@ require('lfs')
 local env = cimport('./src/nvim/os/os.h')
 
 describe('env function', function()
-  function os_setenv(name, value, override)
+  local function os_setenv(name, value, override)
     return env.os_setenv((to_cstr(name)), (to_cstr(value)), override)
   end
 
-  function os_unsetenv(name, value, override)
+  local function os_unsetenv(name, _, _)
     return env.os_unsetenv((to_cstr(name)))
   end
 
-  function os_getenv(name)
+  local function os_getenv(name)
     local rval = env.os_getenv((to_cstr(name)))
     if rval ~= NULL then
       return ffi.string(rval)
diff --git a/test/unit/os/fs_spec.lua b/test/unit/os/fs_spec.lua
index c7a1f55b5d..5a1b9e3aa8 100644
--- a/test/unit/os/fs_spec.lua
+++ b/test/unit/os/fs_spec.lua
@@ -1,3 +1,6 @@
+local lfs = require('lfs')
+local bit = require('bit')
+
 local helpers = require('test.unit.helpers')
 
 local cimport = helpers.cimport
@@ -6,16 +9,12 @@ local internalize = helpers.internalize
 local eq = helpers.eq
 local neq = helpers.neq
 local ffi = helpers.ffi
-local lib = helpers.lib
 local cstr = helpers.cstr
 local to_cstr = helpers.to_cstr
 local OK = helpers.OK
 local FAIL = helpers.FAIL
 local NULL = helpers.NULL
 
-require('lfs')
-require('bit')
-
 cimport('unistd.h')
 cimport('./src/nvim/os/shell.h')
 cimport('./src/nvim/option_defs.h')
@@ -26,8 +25,7 @@ cppimport('sys/stat.h')
 cppimport('sys/fcntl.h')
 cppimport('sys/errno.h')
 
-local len = 0
-local buf = ""
+local buffer = ""
 local directory = nil
 local absolute_executable = nil
 local executable_name = nil
@@ -85,24 +83,26 @@ describe('fs function', function()
   end)
 
   describe('os_dirname', function()
+    local length
+
     local function os_dirname(buf, len)
       return fs.os_dirname(buf, len)
     end
 
     before_each(function()
-      len = (string.len(lfs.currentdir())) + 1
-      buf = cstr(len, '')
+      length = (string.len(lfs.currentdir())) + 1
+      buffer = cstr(length, '')
     end)
 
     it('returns OK and writes current directory into the buffer if it is large\n    enough', function()
-      eq(OK, (os_dirname(buf, len)))
-      eq(lfs.currentdir(), (ffi.string(buf)))
+      eq(OK, (os_dirname(buffer, length)))
+      eq(lfs.currentdir(), (ffi.string(buffer)))
     end)
 
     -- What kind of other failing cases are possible?
     it('returns FAIL if the buffer is too small', function()
-      local buf = cstr((len - 1), '')
-      eq(FAIL, (os_dirname(buf, (len - 1))))
+      local buf = cstr((length - 1), '')
+      eq(FAIL, (os_dirname(buf, (length - 1))))
     end)
   end)
 
@@ -213,15 +213,6 @@ describe('fs function', function()
       os_setperm('unit-test-directory/test.file', orig_test_file_perm)
     end)
 
-    local function os_getperm(filename)
-      local perm = fs.os_getperm((to_cstr(filename)))
-      return tonumber(perm)
-    end
-
-    local function os_setperm(filename, perm)
-      return fs.os_setperm((to_cstr(filename)), perm)
-    end
-
     local function os_fchown(filename, user_id, group_id)
       local fd = ffi.C.open(filename, 0)
       local res = fs.os_fchown(fd, user_id, group_id)
@@ -611,7 +602,7 @@ describe('fs function', function()
 
       it('removes the given directory and returns 0', function()
         lfs.mkdir('unit-test-directory/new-dir')
-        eq(0, (os_rmdir('unit-test-directory/new-dir', mode)))
+        eq(0, os_rmdir('unit-test-directory/new-dir'))
         eq(false, (os_isdir('unit-test-directory/new-dir')))
       end)
     end)
diff --git a/test/unit/os/shell_spec.lua b/test/unit/os/shell_spec.lua
index 20cfc17950..01deefab0c 100644
--- a/test/unit/os/shell_spec.lua
+++ b/test/unit/os/shell_spec.lua
@@ -17,7 +17,7 @@ local shell = helpers.cimport(
   './src/nvim/main.h',
   './src/nvim/misc1.h'
 )
-local ffi, eq, neq = helpers.ffi, helpers.eq, helpers.neq
+local ffi, eq = helpers.ffi, helpers.eq
 local intern = helpers.internalize
 local to_cstr = helpers.to_cstr
 local NULL = ffi.cast('void *', 0)
@@ -70,7 +70,7 @@ describe('shell functions', function()
     end)
 
     it ('returns non-zero exit code', function()
-      local status, output = os_system('exit 2')
+      local status = os_system('exit 2')
       eq(2, status)
     end)
   end)
diff --git a/test/unit/os/users_spec.lua b/test/unit/os/users_spec.lua
index df5d2365c6..236481e9e7 100644
--- a/test/unit/os/users_spec.lua
+++ b/test/unit/os/users_spec.lua
@@ -1,26 +1,24 @@
 local helpers = require('test.unit.helpers')
 
 local cimport = helpers.cimport
-local internalize = helpers.internalize
 local eq = helpers.eq
 local ffi = helpers.ffi
 local lib = helpers.lib
-local cstr = helpers.cstr
 local NULL = helpers.NULL
 local OK = helpers.OK
 local FAIL = helpers.FAIL
 
 local users = cimport('./src/nvim/os/os.h', 'unistd.h')
 
-function garray_new()
+local function garray_new()
   return ffi.new('garray_T[1]')
 end
 
-function garray_get_len(array)
+local function garray_get_len(array)
   return array[0].ga_len
 end
 
-function garray_get_item(array, index)
+local function garray_get_item(array, index)
   return (ffi.cast('void **', array[0].ga_data))[index]
 end
 
diff --git a/test/unit/path_spec.lua b/test/unit/path_spec.lua
index 239a255151..9b76834383 100644
--- a/test/unit/path_spec.lua
+++ b/test/unit/path_spec.lua
@@ -1,18 +1,16 @@
+local lfs = require('lfs')
 local helpers = require('test.unit.helpers')
 
 local cimport = helpers.cimport
-local internalize = helpers.internalize
 local eq = helpers.eq
 local neq = helpers.neq
 local ffi = helpers.ffi
-local lib = helpers.lib
 local cstr = helpers.cstr
 local to_cstr = helpers.to_cstr
 local NULL = helpers.NULL
 local OK = helpers.OK
 local FAIL = helpers.FAIL
 
-require('lfs')
 cimport('string.h')
 local path = cimport('./src/nvim/path.h')
 
@@ -23,7 +21,7 @@ local kBothFilesMissing = path.kBothFilesMissing
 local kOneFileMissing = path.kOneFileMissing
 local kEqualFileNames = path.kEqualFileNames
 
-local len = 0
+local length = 0
 local buffer = nil
 
 describe('path function', function()
@@ -36,19 +34,19 @@ describe('path function', function()
       lfs.rmdir('unit-test-directory')
     end)
 
-    function path_full_dir_name(directory, buffer, len)
+    local function path_full_dir_name(directory, buf, len)
       directory = to_cstr(directory)
-      return path.path_full_dir_name(directory, buffer, len)
+      return path.path_full_dir_name(directory, buf, len)
     end
 
     before_each(function()
       -- Create empty string buffer which will contain the resulting path.
-      len = (string.len(lfs.currentdir())) + 22
-      buffer = cstr(len, '')
+      length = string.len(lfs.currentdir()) + 22
+      buffer = cstr(length, '')
     end)
 
     it('returns the absolute directory name of a given relative one', function()
-      local result = path_full_dir_name('..', buffer, len)
+      local result = path_full_dir_name('..', buffer, length)
       eq(OK, result)
       local old_dir = lfs.currentdir()
       lfs.chdir('..')
@@ -58,23 +56,23 @@ describe('path function', function()
     end)
 
     it('returns the current directory name if the given string is empty', function()
-      eq(OK, (path_full_dir_name('', buffer, len)))
+      eq(OK, (path_full_dir_name('', buffer, length)))
       eq(lfs.currentdir(), (ffi.string(buffer)))
     end)
 
     it('fails if the given directory does not exist', function()
-      eq(FAIL, path_full_dir_name('does_not_exist', buffer, len))
+      eq(FAIL, path_full_dir_name('does_not_exist', buffer, length))
     end)
 
     it('works with a normal relative dir', function()
-      local result = path_full_dir_name('unit-test-directory', buffer, len)
+      local result = path_full_dir_name('unit-test-directory', buffer, length)
       eq(lfs.currentdir() .. '/unit-test-directory', (ffi.string(buffer)))
       eq(OK, result)
     end)
   end)
 
   describe('path_full_compare', function()
-    function path_full_compare(s1, s2, cn)
+    local function path_full_compare(s1, s2, cn)
       s1 = to_cstr(s1)
       s2 = to_cstr(s2)
       return path.path_full_compare(s1, s2, cn or 0)
@@ -117,7 +115,7 @@ describe('path function', function()
   end)
 
   describe('path_tail', function()
-    function path_tail(file)
+    local function path_tail(file)
       local res = path.path_tail((to_cstr(file)))
       neq(NULL, res)
       return ffi.string(res)
@@ -133,7 +131,7 @@ describe('path function', function()
   end)
 
   describe('path_tail_with_sep', function()
-    function path_tail_with_sep(file)
+    local function path_tail_with_sep(file)
       local res = path.path_tail_with_sep((to_cstr(file)))
       neq(NULL, res)
       return ffi.string(res)
@@ -165,7 +163,7 @@ describe('path function', function()
     -- Returns the path tail and length (out param) of the tail.
     -- Does not convert the tail from C-pointer to lua string for use with
     -- strcmp.
-    function invocation_path_tail(invk)
+    local function invocation_path_tail(invk)
       local plen = ffi.new('size_t[?]', 1)
       local ptail = path.invocation_path_tail((to_cstr(invk)), plen)
       neq(NULL, ptail)
@@ -178,7 +176,7 @@ describe('path function', function()
     end
 
     -- This test mimics the intended use in C.
-    function compare(base, pinvk, len)
+    local function compare(base, pinvk, len)
       return eq(0, (ffi.C.strncmp((to_cstr(base)), pinvk, len)))
     end
 
@@ -207,7 +205,7 @@ describe('path function', function()
     end)
 
     it('only accepts whitespace as a terminator for the executable name', function()
-      local invk, len = invocation_path_tail('exe-a+b_c[]()|#!@$%^&*')
+      local invk, _ = invocation_path_tail('exe-a+b_c[]()|#!@$%^&*')
       eq('exe-a+b_c[]()|#!@$%^&*', (ffi.string(invk)))
     end)
 
@@ -215,20 +213,20 @@ describe('path function', function()
       local ptail = path.path_tail(to_cstr("a/b/c x y z"))
       neq(NULL, ptail)
       local tail = ffi.string(ptail)
-      local invk, len = invocation_path_tail("a/b/c x y z")
+      local invk, _ = invocation_path_tail("a/b/c x y z")
       eq(tail, ffi.string(invk))
     end)
 
     it('is not equivalent to path_tail when args contain a path separator', function()
       local ptail = path.path_tail(to_cstr("a/b/c x y/z"))
       neq(NULL, ptail)
-      local invk, len = invocation_path_tail("a/b/c x y/z")
+      local invk, _ = invocation_path_tail("a/b/c x y/z")
       neq((ffi.string(ptail)), (ffi.string(invk)))
     end)
   end)
 
   describe('path_next_component', function()
-    function path_next_component(file)
+    local function path_next_component(file)
       local res = path.path_next_component((to_cstr(file)))
       neq(NULL, res)
       return ffi.string(res)
@@ -308,11 +306,11 @@ describe('more path function', function()
 
     -- Since the tests are executed, they are called by an executable. We use
     -- that executable for several asserts.
-    absolute_executable = arg[0]
+    local absolute_executable = arg[0]
 
     -- Split absolute_executable into a directory and the actual file name for
     -- later usage.
-    directory, executable_name = string.match(absolute_executable, '^(.*)/(.*)$')
+    local directory, executable_name = string.match(absolute_executable, '^(.*)/(.*)$')  -- luacheck: ignore
   end)
 
   teardown(function()
@@ -321,27 +319,27 @@ describe('more path function', function()
   end)
 
   describe('vim_FullName', function()
-    function vim_FullName(filename, buffer, length, force)
+    local function vim_FullName(filename, buf, len, force)
       filename = to_cstr(filename)
-      return path.vim_FullName(filename, buffer, length, force)
+      return path.vim_FullName(filename, buf, len, force)
     end
 
     before_each(function()
       -- Create empty string buffer which will contain the resulting path.
-      len = (string.len(lfs.currentdir())) + 33
-      buffer = cstr(len, '')
+      length = (string.len(lfs.currentdir())) + 33
+      buffer = cstr(length, '')
     end)
 
     it('fails if given filename is NULL', function()
       local force_expansion = 1
-      local result = path.vim_FullName(NULL, buffer, len, force_expansion)
+      local result = path.vim_FullName(NULL, buffer, length, force_expansion)
       eq(FAIL, result)
     end)
 
     it('uses the filename if the filename is a URL', function()
       local force_expansion = 1
       local filename = 'http://www.neovim.org'
-      local result = vim_FullName(filename, buffer, len, force_expansion)
+      local result = vim_FullName(filename, buffer, length, force_expansion)
       eq(filename, (ffi.string(buffer)))
       eq(OK, result)
     end)
@@ -349,14 +347,14 @@ describe('more path function', function()
     it('fails and uses filename if given filename contains non-existing directory', function()
       local force_expansion = 1
       local filename = 'non_existing_dir/test.file'
-      local result = vim_FullName(filename, buffer, len, force_expansion)
+      local result = vim_FullName(filename, buffer, length, force_expansion)
       eq(filename, (ffi.string(buffer)))
       eq(FAIL, result)
     end)
 
     it('concatenates given filename if it does not contain a slash', function()
       local force_expansion = 1
-      local result = vim_FullName('test.file', buffer, len, force_expansion)
+      local result = vim_FullName('test.file', buffer, length, force_expansion)
       local expected = lfs.currentdir() .. '/test.file'
       eq(expected, (ffi.string(buffer)))
       eq(OK, result)
@@ -364,7 +362,7 @@ describe('more path function', function()
 
     it('concatenates given filename if it is a directory but does not contain a\n    slash', function()
       local force_expansion = 1
-      local result = vim_FullName('..', buffer, len, force_expansion)
+      local result = vim_FullName('..', buffer, length, force_expansion)
       local expected = lfs.currentdir() .. '/..'
       eq(expected, (ffi.string(buffer)))
       eq(OK, result)
@@ -374,7 +372,7 @@ describe('more path function', function()
     -- the unit tests? Which other directory would be better?
     it('enters given directory (instead of just concatenating the strings) if possible and if path contains a slash', function()
       local force_expansion = 1
-      local result = vim_FullName('../test.file', buffer, len, force_expansion)
+      local result = vim_FullName('../test.file', buffer, length, force_expansion)
       local old_dir = lfs.currentdir()
       lfs.chdir('..')
       local expected = lfs.currentdir() .. '/test.file'
@@ -386,7 +384,7 @@ describe('more path function', function()
     it('just copies the path if it is already absolute and force=0', function()
       local force_expansion = 0
       local absolute_path = '/absolute/path'
-      local result = vim_FullName(absolute_path, buffer, len, force_expansion)
+      local result = vim_FullName(absolute_path, buffer, length, force_expansion)
       eq(absolute_path, (ffi.string(buffer)))
       eq(OK, result)
     end)
@@ -394,14 +392,14 @@ describe('more path function', function()
     it('fails and uses filename when the path is relative to HOME', function()
       local force_expansion = 1
       local absolute_path = '~/home.file'
-      local result = vim_FullName(absolute_path, buffer, len, force_expansion)
+      local result = vim_FullName(absolute_path, buffer, length, force_expansion)
       eq(absolute_path, (ffi.string(buffer)))
       eq(FAIL, result)
     end)
 
     it('works with some "normal" relative path with directories', function()
       local force_expansion = 1
-      local result = vim_FullName('unit-test-directory/test.file', buffer, len, force_expansion)
+      local result = vim_FullName('unit-test-directory/test.file', buffer, length, force_expansion)
       eq(OK, result)
       eq(lfs.currentdir() .. '/unit-test-directory/test.file', (ffi.string(buffer)))
     end)
@@ -411,7 +409,7 @@ describe('more path function', function()
       local filename = to_cstr('unit-test-directory/test.file')
       -- Don't use the wrapper here but pass a cstring directly to the c
       -- function.
-      local result = path.vim_FullName(filename, buffer, len, force_expansion)
+      local result = path.vim_FullName(filename, buffer, length, force_expansion)
       eq(lfs.currentdir() .. '/unit-test-directory/test.file', (ffi.string(buffer)))
       eq('unit-test-directory/test.file', (ffi.string(filename)))
       eq(OK, result)
@@ -420,15 +418,15 @@ describe('more path function', function()
     it('works with directories that have one path component', function()
       local force_expansion = 1
       local filename = to_cstr('/tmp')
-      local result = path.vim_FullName(filename, buffer, len, force_expansion)
+      local result = path.vim_FullName(filename, buffer, length, force_expansion)
       eq('/tmp', ffi.string(buffer))
       eq(OK, result)
     end)
   end)
 
   describe('path_fix_case', function()
-    function fix_case(file)
-      c_file = to_cstr(file)
+    local function fix_case(file)
+      local c_file = to_cstr(file)
       path.path_fix_case(c_file)
       return ffi.string(c_file)
     end
@@ -493,7 +491,7 @@ describe('more path function', function()
   end)
 
   describe('path_is_absolute_path', function()
-    function path_is_absolute_path(filename)
+    local function path_is_absolute_path(filename)
       filename = to_cstr(filename)
       return path.path_is_absolute_path(filename)
     end
diff --git a/test/unit/preprocess.lua b/test/unit/preprocess.lua
index d4c2e088a4..e5c838b13b 100644
--- a/test/unit/preprocess.lua
+++ b/test/unit/preprocess.lua
@@ -169,8 +169,8 @@ local type_to_class = {
 -- find the best cc. If os.exec causes problems on windows (like popping up
 -- a console window) we might consider using something like this:
 -- http://scite-ru.googlecode.com/svn/trunk/pack/tools/LuaLib/shell.html#exec
-local function find_best_cc(ccs)
-  for _, meta in pairs(ccs) do
+local function find_best_cc(compilers)
+  for _, meta in pairs(compilers) do
     local version = io.popen(tostring(meta.path) .. " -v 2>&1")
     version:close()
     if version then
diff --git a/test/unit/profile_spec.lua b/test/unit/profile_spec.lua
index 2b006a0768..852475fe2c 100644
--- a/test/unit/profile_spec.lua
+++ b/test/unit/profile_spec.lua
@@ -36,20 +36,20 @@ local function cmp_assert(v1, v2, op, opstr)
   assert.is_true(res)
 end
 
-local function lt(v1, v2)
-  cmp_assert(v1, v2, function(v1, v2) return v1 < v2 end, "<")
+local function lt(a, b)  -- luacheck: ignore
+  cmp_assert(a, b, function(x, y) return x < y end, "<")
 end
 
-local function lte(v1, v2)
-  cmp_assert(v1, v2, function(v1, v2) return v1 <= v2 end, "<=")
+local function lte(a, b)  -- luacheck: ignore
+  cmp_assert(a, b, function(x, y) return x <= y end, "<=")
 end
 
-local function gt(v1, v2)
-  cmp_assert(v1, v2, function(v1, v2) return v1 > v2 end, ">")
+local function gt(a, b)  -- luacheck: ignore
+  cmp_assert(a, b, function(x, y) return x > y end, ">")
 end
 
-local function gte(v1, v2)
-  cmp_assert(v1, v2, function(v1, v2) return v1 >= v2 end, ">=")
+local function gte(a, b)
+  cmp_assert(a, b, function(x, y) return x >= y end, ">=")
 end
 
 -- missing functions:
@@ -70,7 +70,7 @@ describe('profiling related functions', function()
   local function profile_equal(t1, t2) return prof.profile_equal(t1, t2) end
   local function profile_msg(t) return ffi.string(prof.profile_msg(t)) end
 
-  local function toseconds(t)
+  local function toseconds(t)  -- luacheck: ignore
     local str = trim(profile_msg(t))
     local spl = split(str, ".")
     local s, us = spl[1], spl[2]
@@ -122,7 +122,7 @@ describe('profiling related functions', function()
       local divided = profile_divide(start, divisor)
 
       local res = divided
-      for i = 1, divisor - 1 do
+      for _ = 1, divisor - 1 do
         res = profile_add(res, divided)
       end
 
@@ -143,7 +143,7 @@ describe('profiling related functions', function()
   describe('profile_start', function()
     it('increases', function()
       local last = profile_start()
-      for i=1,100 do
+      for _ = 1, 100 do
         local curr = profile_start()
         gte(curr, last)
         last = curr
@@ -157,7 +157,7 @@ describe('profiling related functions', function()
     end)
 
     it('outer elapsed >= inner elapsed', function()
-      for i = 1, 100 do
+      for _ = 1, 100 do
         local start_outer = profile_start()
         local start_inner = profile_start()
         local elapsed_inner = profile_end(start_inner)
@@ -238,7 +238,7 @@ describe('profiling related functions', function()
       -- t2 >= t1 => profile_cmp(t1, t2) >= 0
       assert.is_true(cmp >= 0)
 
-      local cmp = profile_cmp(profile_sub(start3, start1), profile_sub(start2, start1))
+      cmp = profile_cmp(profile_sub(start3, start1), profile_sub(start2, start1))
       -- t2 <= t1 => profile_cmp(t1, t2) <= 0
       assert.is_true(cmp <= 0)
     end)
diff --git a/test/unit/set.lua b/test/unit/set.lua
index bfb6b8c41c..4e66546f32 100644
--- a/test/unit/set.lua
+++ b/test/unit/set.lua
@@ -35,7 +35,7 @@ end
 
 -- adds the argument table to this Set
 function Set:union_table(t)
-  for k, v in pairs(t) do
+  for _, v in pairs(t) do
     self:add(v)
   end
 end