refactor(test): rename alter_slashes, invert its behavior

- `alter_slashes` belongs in `testutil.lua`, not `testnvim.lua`.
- `alter_slashes` is an unusual name. Rename it to `fix_slashes`.
- invert its behavior, to emphasize that `/` slashes are the preferred,
  pervasive convention, not `\` slashes.

11 files changed, 300 insertions, 307 deletions

diff --git a/test/functional/api/vim_spec.lua b/test/functional/api/vim_spec.lua
index 074d3ac0a3..71703c9b05 100644
--- a/test/functional/api/vim_spec.lua
+++ b/test/functional/api/vim_spec.lua
@@ -3201,7 +3201,7 @@ describe('API', function()
   end)
 
   describe('nvim_get_runtime_file', function()
-    local p = n.alter_slashes
+    local p = t.fix_slashes
     it('can find files', function()
       eq({}, api.nvim_get_runtime_file('bork.borkbork', false))
       eq({}, api.nvim_get_runtime_file('bork.borkbork', true))
@@ -3210,36 +3210,36 @@ describe('API', function()
       local val = api.nvim_get_runtime_file('autoload/remote/*.vim', true)
       eq(2, #val)
       if endswith(val[1], 'define.vim') then
-        ok(endswith(val[1], p 'autoload/remote/define.vim'))
-        ok(endswith(val[2], p 'autoload/remote/host.vim'))
+        ok(endswith(p(val[1]), 'autoload/remote/define.vim'))
+        ok(endswith(p(val[2]), 'autoload/remote/host.vim'))
       else
-        ok(endswith(val[1], p 'autoload/remote/host.vim'))
-        ok(endswith(val[2], p 'autoload/remote/define.vim'))
+        ok(endswith(p(val[1]), 'autoload/remote/host.vim'))
+        ok(endswith(p(val[2]), 'autoload/remote/define.vim'))
       end
       val = api.nvim_get_runtime_file('autoload/remote/*.vim', false)
       eq(1, #val)
       ok(
-        endswith(val[1], p 'autoload/remote/define.vim')
-          or endswith(val[1], p 'autoload/remote/host.vim')
+        endswith(p(val[1]), 'autoload/remote/define.vim')
+          or endswith(p(val[1]), 'autoload/remote/host.vim')
       )
 
       val = api.nvim_get_runtime_file('lua', true)
       eq(1, #val)
-      ok(endswith(val[1], p 'lua'))
+      ok(endswith(p(val[1]), 'lua'))
 
       val = api.nvim_get_runtime_file('lua/vim', true)
       eq(1, #val)
-      ok(endswith(val[1], p 'lua/vim'))
+      ok(endswith(p(val[1]), 'lua/vim'))
     end)
 
     it('can find directories', function()
       local val = api.nvim_get_runtime_file('lua/', true)
       eq(1, #val)
-      ok(endswith(val[1], p 'lua/'))
+      ok(endswith(p(val[1]), 'lua/'))
 
       val = api.nvim_get_runtime_file('lua/vim/', true)
       eq(1, #val)
-      ok(endswith(val[1], p 'lua/vim/'))
+      ok(endswith(p(val[1]), 'lua/vim/'))
 
       eq({}, api.nvim_get_runtime_file('foobarlang/', true))
     end)
diff --git a/test/functional/autocmd/dirchanged_spec.lua b/test/functional/autocmd/dirchanged_spec.lua
index 24ac737b5b..1cde0e0552 100644
--- a/test/functional/autocmd/dirchanged_spec.lua
+++ b/test/functional/autocmd/dirchanged_spec.lua
@@ -9,7 +9,7 @@ local request = n.request
 local is_os = t.is_os
 
 describe('autocmd DirChanged and DirChangedPre', function()
-  local curdir = vim.uv.cwd():gsub('\\', '/')
+  local curdir = t.fix_slashes(vim.uv.cwd())
   local dirs = {
     curdir .. '/Xtest-functional-autocmd-dirchanged.dir1',
     curdir .. '/Xtest-functional-autocmd-dirchanged.dir2',
diff --git a/test/functional/core/startup_spec.lua b/test/functional/core/startup_spec.lua
index 8d6ba9712a..f48bcb9360 100644
--- a/test/functional/core/startup_spec.lua
+++ b/test/functional/core/startup_spec.lua
@@ -27,7 +27,6 @@ local sleep = vim.uv.sleep
 local startswith = vim.startswith
 local write_file = t.write_file
 local api = n.api
-local alter_slashes = n.alter_slashes
 local is_os = t.is_os
 local dedent = t.dedent
 local tbl_map = vim.tbl_map
@@ -40,22 +39,15 @@ local testlog = 'Xtest-startupspec-log'
 describe('startup', function()
   it('--clean', function()
     clear()
-    ok(
-      string.find(
-        alter_slashes(api.nvim_get_option_value('runtimepath', {})),
-        fn.stdpath('config'),
-        1,
-        true
-      ) ~= nil
+    matches(
+      vim.pesc(t.fix_slashes(fn.stdpath('config'))),
+      t.fix_slashes(api.nvim_get_option_value('runtimepath', {}))
     )
+
     clear('--clean')
     ok(
-      string.find(
-        alter_slashes(api.nvim_get_option_value('runtimepath', {})),
-        fn.stdpath('config'),
-        1,
-        true
-      ) == nil
+      not t.fix_slashes(api.nvim_get_option_value('runtimepath', {}))
+        :match(vim.pesc(t.fix_slashes(fn.stdpath('config'))))
     )
   end)
 
diff --git a/test/functional/ex_cmds/mksession_spec.lua b/test/functional/ex_cmds/mksession_spec.lua
index 9b24854362..8f09e802eb 100644
--- a/test/functional/ex_cmds/mksession_spec.lua
+++ b/test/functional/ex_cmds/mksession_spec.lua
@@ -170,7 +170,7 @@ describe(':mksession', function()
     skip(is_os('win'), 'causes rmdir() to fail')
 
     local cwd_dir = fn.fnamemodify('.', ':p:~'):gsub([[[\/]*$]], '')
-    cwd_dir = cwd_dir:gsub([[\]], '/') -- :mksession always uses unix slashes.
+    cwd_dir = t.fix_slashes(cwd_dir) -- :mksession always uses unix slashes.
     local session_path = cwd_dir .. '/' .. session_file
 
     command('cd ' .. tab_dir)
diff --git a/test/functional/lua/uri_spec.lua b/test/functional/lua/uri_spec.lua
index 553afb35d3..258b96bc43 100644
--- a/test/functional/lua/uri_spec.lua
+++ b/test/functional/lua/uri_spec.lua
@@ -217,7 +217,7 @@ describe('URI methods', function()
         ]],
         file
       )
-      local expected_uri = 'file:///' .. file:gsub('\\', '/')
+      local expected_uri = 'file:///' .. t.fix_slashes(file)
       eq(expected_uri, exec_lua(test_case))
       os.remove(file)
     end)
diff --git a/test/functional/options/autochdir_spec.lua b/test/functional/options/autochdir_spec.lua
index c490ab67a9..a409262d84 100644
--- a/test/functional/options/autochdir_spec.lua
+++ b/test/functional/options/autochdir_spec.lua
@@ -22,7 +22,7 @@ describe("'autochdir'", function()
   end)
 
   it('is not overwritten by getwinvar() call #17609', function()
-    local curdir = vim.uv.cwd():gsub('\\', '/')
+    local curdir = t.fix_slashes(vim.uv.cwd())
     local dir_a = curdir .. '/Xtest-functional-options-autochdir.dir_a'
     local dir_b = curdir .. '/Xtest-functional-options-autochdir.dir_b'
     mkdir(dir_a)
diff --git a/test/functional/options/defaults_spec.lua b/test/functional/options/defaults_spec.lua
index ad94ef1206..43c9768776 100644
--- a/test/functional/options/defaults_spec.lua
+++ b/test/functional/options/defaults_spec.lua
@@ -23,7 +23,6 @@ local insert = n.insert
 local neq = t.neq
 local mkdir = t.mkdir
 local rmdir = n.rmdir
-local alter_slashes = n.alter_slashes
 local tbl_contains = vim.tbl_contains
 local expect_exit = n.expect_exit
 local check_close = n.check_close
@@ -262,7 +261,7 @@ describe('startup defaults', function()
           NVIM_LOG_FILE = '', -- Empty is invalid.
         },
       })
-      eq(xdgstatedir .. '/log', string.gsub(eval('$NVIM_LOG_FILE'), '\\', '/'))
+      eq(xdgstatedir .. '/log', t.fix_slashes(eval('$NVIM_LOG_FILE')))
     end)
 
     it('defaults to stdpath("log")/log if invalid', function()
@@ -273,7 +272,7 @@ describe('startup defaults', function()
           NVIM_LOG_FILE = '.', -- Any directory is invalid.
         },
       })
-      eq(xdgstatedir .. '/log', string.gsub(eval('$NVIM_LOG_FILE'), '\\', '/'))
+      eq(xdgstatedir .. '/log', t.fix_slashes(eval('$NVIM_LOG_FILE')))
       -- Avoid "failed to open $NVIM_LOG_FILE" noise in test output.
       expect_exit(command, 'qall!')
     end)
@@ -383,69 +382,69 @@ describe('XDG defaults', function()
 
       eq(
         (
-          (
+          t.fix_slashes(
             root_path
-            .. ('/x'):rep(4096)
-            .. '/nvim'
-            .. ','
-            .. root_path
-            .. ('/a'):rep(2048)
-            .. '/nvim'
-            .. ','
-            .. root_path
-            .. ('/b'):rep(2048)
-            .. '/nvim'
-            .. (',' .. root_path .. '/c/nvim')
-            .. ','
-            .. root_path
-            .. ('/X'):rep(4096)
-            .. '/'
-            .. data_dir
-            .. '/site'
-            .. ','
-            .. root_path
-            .. ('/A'):rep(2048)
-            .. '/nvim/site'
-            .. ','
-            .. root_path
-            .. ('/B'):rep(2048)
-            .. '/nvim/site'
-            .. (',' .. root_path .. '/C/nvim/site')
-            .. ','
-            .. vimruntime
-            .. ','
-            .. libdir
-            .. (',' .. root_path .. '/C/nvim/site/after')
-            .. ','
-            .. root_path
-            .. ('/B'):rep(2048)
-            .. '/nvim/site/after'
-            .. ','
-            .. root_path
-            .. ('/A'):rep(2048)
-            .. '/nvim/site/after'
-            .. ','
-            .. root_path
-            .. ('/X'):rep(4096)
-            .. '/'
-            .. data_dir
-            .. '/site/after'
-            .. (',' .. root_path .. '/c/nvim/after')
-            .. ','
-            .. root_path
-            .. ('/b'):rep(2048)
-            .. '/nvim/after'
-            .. ','
-            .. root_path
-            .. ('/a'):rep(2048)
-            .. '/nvim/after'
-            .. ','
-            .. root_path
-            .. ('/x'):rep(4096)
-            .. '/nvim/after'
-          ):gsub('\\', '/')
+              .. ('/x'):rep(4096)
+              .. '/nvim'
+              .. ','
+              .. root_path
+              .. ('/a'):rep(2048)
+              .. '/nvim'
+              .. ','
+              .. root_path
+              .. ('/b'):rep(2048)
+              .. '/nvim'
+              .. (',' .. root_path .. '/c/nvim')
+              .. ','
+              .. root_path
+              .. ('/X'):rep(4096)
+              .. '/'
+              .. data_dir
+              .. '/site'
+              .. ','
+              .. root_path
+              .. ('/A'):rep(2048)
+              .. '/nvim/site'
+              .. ','
+              .. root_path
+              .. ('/B'):rep(2048)
+              .. '/nvim/site'
+              .. (',' .. root_path .. '/C/nvim/site')
+              .. ','
+              .. vimruntime
+              .. ','
+              .. libdir
+              .. (',' .. root_path .. '/C/nvim/site/after')
+              .. ','
+              .. root_path
+              .. ('/B'):rep(2048)
+              .. '/nvim/site/after'
+              .. ','
+              .. root_path
+              .. ('/A'):rep(2048)
+              .. '/nvim/site/after'
+              .. ','
+              .. root_path
+              .. ('/X'):rep(4096)
+              .. '/'
+              .. data_dir
+              .. '/site/after'
+              .. (',' .. root_path .. '/c/nvim/after')
+              .. ','
+              .. root_path
+              .. ('/b'):rep(2048)
+              .. '/nvim/after'
+              .. ','
+              .. root_path
+              .. ('/a'):rep(2048)
+              .. '/nvim/after'
+              .. ','
+              .. root_path
+              .. ('/x'):rep(4096)
+              .. '/nvim/after'
+          )
         ),
-        (api.nvim_get_option_value('runtimepath', {})):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('runtimepath', {}))
       )
       command('set runtimepath&')
       command('set backupdir&')
@@ -454,85 +453,85 @@ describe('XDG defaults', function()
       command('set viewdir&')
       eq(
         (
-          (
+          t.fix_slashes(
             root_path
-            .. ('/x'):rep(4096)
-            .. '/nvim'
-            .. ','
-            .. root_path
-            .. ('/a'):rep(2048)
-            .. '/nvim'
-            .. ','
-            .. root_path
-            .. ('/b'):rep(2048)
-            .. '/nvim'
-            .. (',' .. root_path .. '/c/nvim')
-            .. ','
-            .. root_path
-            .. ('/X'):rep(4096)
-            .. '/'
-            .. data_dir
-            .. '/site'
-            .. ','
-            .. root_path
-            .. ('/A'):rep(2048)
-            .. '/nvim/site'
-            .. ','
-            .. root_path
-            .. ('/B'):rep(2048)
-            .. '/nvim/site'
-            .. (',' .. root_path .. '/C/nvim/site')
-            .. ','
-            .. vimruntime
-            .. ','
-            .. libdir
-            .. (',' .. root_path .. '/C/nvim/site/after')
-            .. ','
-            .. root_path
-            .. ('/B'):rep(2048)
-            .. '/nvim/site/after'
-            .. ','
-            .. root_path
-            .. ('/A'):rep(2048)
-            .. '/nvim/site/after'
-            .. ','
-            .. root_path
-            .. ('/X'):rep(4096)
-            .. '/'
-            .. data_dir
-            .. '/site/after'
-            .. (',' .. root_path .. '/c/nvim/after')
-            .. ','
-            .. root_path
-            .. ('/b'):rep(2048)
-            .. '/nvim/after'
-            .. ','
-            .. root_path
-            .. ('/a'):rep(2048)
-            .. '/nvim/after'
-            .. ','
-            .. root_path
-            .. ('/x'):rep(4096)
-            .. '/nvim/after'
-          ):gsub('\\', '/')
+              .. ('/x'):rep(4096)
+              .. '/nvim'
+              .. ','
+              .. root_path
+              .. ('/a'):rep(2048)
+              .. '/nvim'
+              .. ','
+              .. root_path
+              .. ('/b'):rep(2048)
+              .. '/nvim'
+              .. (',' .. root_path .. '/c/nvim')
+              .. ','
+              .. root_path
+              .. ('/X'):rep(4096)
+              .. '/'
+              .. data_dir
+              .. '/site'
+              .. ','
+              .. root_path
+              .. ('/A'):rep(2048)
+              .. '/nvim/site'
+              .. ','
+              .. root_path
+              .. ('/B'):rep(2048)
+              .. '/nvim/site'
+              .. (',' .. root_path .. '/C/nvim/site')
+              .. ','
+              .. vimruntime
+              .. ','
+              .. libdir
+              .. (',' .. root_path .. '/C/nvim/site/after')
+              .. ','
+              .. root_path
+              .. ('/B'):rep(2048)
+              .. '/nvim/site/after'
+              .. ','
+              .. root_path
+              .. ('/A'):rep(2048)
+              .. '/nvim/site/after'
+              .. ','
+              .. root_path
+              .. ('/X'):rep(4096)
+              .. '/'
+              .. data_dir
+              .. '/site/after'
+              .. (',' .. root_path .. '/c/nvim/after')
+              .. ','
+              .. root_path
+              .. ('/b'):rep(2048)
+              .. '/nvim/after'
+              .. ','
+              .. root_path
+              .. ('/a'):rep(2048)
+              .. '/nvim/after'
+              .. ','
+              .. root_path
+              .. ('/x'):rep(4096)
+              .. '/nvim/after'
+          )
         ),
-        (api.nvim_get_option_value('runtimepath', {})):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('runtimepath', {}))
       )
       eq(
         '.,' .. root_path .. ('/X'):rep(4096) .. '/' .. state_dir .. '/backup//',
-        (api.nvim_get_option_value('backupdir', {}):gsub('\\', '/'))
+        t.fix_slashes(api.nvim_get_option_value('backupdir', {}))
       )
       eq(
         root_path .. ('/X'):rep(4096) .. '/' .. state_dir .. '/swap//',
-        (api.nvim_get_option_value('directory', {})):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('directory', {}))
       )
       eq(
         root_path .. ('/X'):rep(4096) .. '/' .. state_dir .. '/undo//',
-        (api.nvim_get_option_value('undodir', {})):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('undodir', {}))
       )
       eq(
         root_path .. ('/X'):rep(4096) .. '/' .. state_dir .. '/view//',
-        (api.nvim_get_option_value('viewdir', {})):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('viewdir', {}))
       )
     end)
   end)
@@ -574,26 +573,26 @@ describe('XDG defaults', function()
       local vimruntime, libdir = vimruntime_and_libdir()
       eq(
         (
-          (
+          t.fix_slashes(
             '$XDG_DATA_HOME/nvim'
-            .. ',$XDG_DATA_DIRS/nvim'
-            .. ',$XDG_CONFIG_HOME/'
-            .. data_dir
-            .. '/site'
-            .. ',$XDG_CONFIG_DIRS/nvim/site'
-            .. ','
-            .. vimruntime
-            .. ','
-            .. libdir
-            .. ',$XDG_CONFIG_DIRS/nvim/site/after'
-            .. ',$XDG_CONFIG_HOME/'
-            .. data_dir
-            .. '/site/after'
-            .. ',$XDG_DATA_DIRS/nvim/after'
-            .. ',$XDG_DATA_HOME/nvim/after'
-          ):gsub('\\', '/')
+              .. ',$XDG_DATA_DIRS/nvim'
+              .. ',$XDG_CONFIG_HOME/'
+              .. data_dir
+              .. '/site'
+              .. ',$XDG_CONFIG_DIRS/nvim/site'
+              .. ','
+              .. vimruntime
+              .. ','
+              .. libdir
+              .. ',$XDG_CONFIG_DIRS/nvim/site/after'
+              .. ',$XDG_CONFIG_HOME/'
+              .. data_dir
+              .. '/site/after'
+              .. ',$XDG_DATA_DIRS/nvim/after'
+              .. ',$XDG_DATA_HOME/nvim/after'
+          )
         ),
-        (api.nvim_get_option_value('runtimepath', {})):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('runtimepath', {}))
       )
       command('set runtimepath&')
       command('set backupdir&')
@@ -602,80 +601,80 @@ describe('XDG defaults', function()
       command('set viewdir&')
       eq(
         (
-          (
+          t.fix_slashes(
             '$XDG_DATA_HOME/nvim'
-            .. ',$XDG_DATA_DIRS/nvim'
-            .. ',$XDG_CONFIG_HOME/'
-            .. data_dir
-            .. '/site'
-            .. ',$XDG_CONFIG_DIRS/nvim/site'
-            .. ','
-            .. vimruntime
-            .. ','
-            .. libdir
-            .. ',$XDG_CONFIG_DIRS/nvim/site/after'
-            .. ',$XDG_CONFIG_HOME/'
-            .. data_dir
-            .. '/site/after'
-            .. ',$XDG_DATA_DIRS/nvim/after'
-            .. ',$XDG_DATA_HOME/nvim/after'
-          ):gsub('\\', '/')
+              .. ',$XDG_DATA_DIRS/nvim'
+              .. ',$XDG_CONFIG_HOME/'
+              .. data_dir
+              .. '/site'
+              .. ',$XDG_CONFIG_DIRS/nvim/site'
+              .. ','
+              .. vimruntime
+              .. ','
+              .. libdir
+              .. ',$XDG_CONFIG_DIRS/nvim/site/after'
+              .. ',$XDG_CONFIG_HOME/'
+              .. data_dir
+              .. '/site/after'
+              .. ',$XDG_DATA_DIRS/nvim/after'
+              .. ',$XDG_DATA_HOME/nvim/after'
+          )
         ),
-        (api.nvim_get_option_value('runtimepath', {})):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('runtimepath', {}))
       )
       eq(
         ('.,$XDG_CONFIG_HOME/' .. state_dir .. '/backup//'),
-        api.nvim_get_option_value('backupdir', {}):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('backupdir', {}))
       )
       eq(
         ('$XDG_CONFIG_HOME/' .. state_dir .. '/swap//'),
-        api.nvim_get_option_value('directory', {}):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('directory', {}))
       )
       eq(
         ('$XDG_CONFIG_HOME/' .. state_dir .. '/undo//'),
-        api.nvim_get_option_value('undodir', {}):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('undodir', {}))
       )
       eq(
         ('$XDG_CONFIG_HOME/' .. state_dir .. '/view//'),
-        api.nvim_get_option_value('viewdir', {}):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('viewdir', {}))
       )
       command('set all&')
       eq(
-        (
+        t.fix_slashes(
           '$XDG_DATA_HOME/nvim'
-          .. ',$XDG_DATA_DIRS/nvim'
-          .. ',$XDG_CONFIG_HOME/'
-          .. data_dir
-          .. '/site'
-          .. ',$XDG_CONFIG_DIRS/nvim/site'
-          .. ','
-          .. vimruntime
-          .. ','
-          .. libdir
-          .. ',$XDG_CONFIG_DIRS/nvim/site/after'
-          .. ',$XDG_CONFIG_HOME/'
-          .. data_dir
-          .. '/site/after'
-          .. ',$XDG_DATA_DIRS/nvim/after'
-          .. ',$XDG_DATA_HOME/nvim/after'
-        ):gsub('\\', '/'),
-        (api.nvim_get_option_value('runtimepath', {})):gsub('\\', '/')
+            .. ',$XDG_DATA_DIRS/nvim'
+            .. ',$XDG_CONFIG_HOME/'
+            .. data_dir
+            .. '/site'
+            .. ',$XDG_CONFIG_DIRS/nvim/site'
+            .. ','
+            .. vimruntime
+            .. ','
+            .. libdir
+            .. ',$XDG_CONFIG_DIRS/nvim/site/after'
+            .. ',$XDG_CONFIG_HOME/'
+            .. data_dir
+            .. '/site/after'
+            .. ',$XDG_DATA_DIRS/nvim/after'
+            .. ',$XDG_DATA_HOME/nvim/after'
+        ),
+        t.fix_slashes(api.nvim_get_option_value('runtimepath', {}))
       )
       eq(
         ('.,$XDG_CONFIG_HOME/' .. state_dir .. '/backup//'),
-        api.nvim_get_option_value('backupdir', {}):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('backupdir', {}))
       )
       eq(
         ('$XDG_CONFIG_HOME/' .. state_dir .. '/swap//'),
-        api.nvim_get_option_value('directory', {}):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('directory', {}))
       )
       eq(
         ('$XDG_CONFIG_HOME/' .. state_dir .. '/undo//'),
-        api.nvim_get_option_value('undodir', {}):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('undodir', {}))
       )
       eq(
         ('$XDG_CONFIG_HOME/' .. state_dir .. '/view//'),
-        api.nvim_get_option_value('viewdir', {}):gsub('\\', '/')
+        t.fix_slashes(api.nvim_get_option_value('viewdir', {}))
       )
       eq(nil, (fn.tempname()):match('XDG_RUNTIME_DIR'))
     end)
@@ -939,7 +938,7 @@ describe('stdpath()', function()
         local child = vim.fn.jobstart({ vim.v.progpath, '--clean', '--headless', '--listen', 'x', '+qall!' }, { env = { NVIM_APPNAME = %q } })
         return vim.fn.jobwait({ child }, %d)[1]
       ]],
-        alter_slashes(testAppname),
+        testAppname,
         3000
       )
       eq(expected_exitcode, exec_lua(lua_code))
@@ -970,7 +969,7 @@ describe('stdpath()', function()
       },
     })
 
-    t.matches(vim.pesc(tmpdir), fn.tempname():gsub('\\', '/'))
+    t.matches(vim.pesc(tmpdir), t.fix_slashes(fn.tempname()))
     t.assert_nolog('tempdir', testlog, 100)
     t.assert_nolog('TMPDIR', testlog, 100)
     t.matches([=[[/\\]relative%-appname.[^/\\]+]=], api.nvim_get_vvar('servername'))
@@ -981,19 +980,19 @@ describe('stdpath()', function()
       it('knows XDG_CONFIG_HOME', function()
         clear({
           env = {
-            XDG_CONFIG_HOME = alter_slashes('/home/docwhat/.config'),
+            XDG_CONFIG_HOME = '/home/docwhat/.config',
           },
         })
-        eq(alter_slashes('/home/docwhat/.config/nvim'), fn.stdpath('config'))
+        eq('/home/docwhat/.config/nvim', t.fix_slashes(fn.stdpath('config')))
       end)
 
       it('handles changes during runtime', function()
         clear({ env = {
-          XDG_CONFIG_HOME = alter_slashes('/home/original'),
+          XDG_CONFIG_HOME = '/home/original',
         } })
-        eq(alter_slashes('/home/original/nvim'), fn.stdpath('config'))
-        command("let $XDG_CONFIG_HOME='" .. alter_slashes('/home/new') .. "'")
-        eq(alter_slashes('/home/new/nvim'), fn.stdpath('config'))
+        eq('/home/original/nvim', t.fix_slashes(fn.stdpath('config')))
+        command("let $XDG_CONFIG_HOME='/home/new'")
+        eq('/home/new/nvim', t.fix_slashes(fn.stdpath('config')))
       end)
 
       it("doesn't expand $VARIABLES", function()
@@ -1003,32 +1002,32 @@ describe('stdpath()', function()
             VARIABLES = 'this-should-not-happen',
           },
         })
-        eq(alter_slashes('$VARIABLES/nvim'), fn.stdpath('config'))
+        eq('$VARIABLES/nvim', t.fix_slashes(fn.stdpath('config')))
       end)
 
       it("doesn't expand ~/", function()
         clear({ env = {
-          XDG_CONFIG_HOME = alter_slashes('~/frobnitz'),
+          XDG_CONFIG_HOME = '~/frobnitz',
         } })
-        eq(alter_slashes('~/frobnitz/nvim'), fn.stdpath('config'))
+        eq('~/frobnitz/nvim', t.fix_slashes(fn.stdpath('config')))
       end)
     end)
 
     describe('with "data"', function()
       it('knows XDG_DATA_HOME', function()
         clear({ env = {
-          XDG_DATA_HOME = alter_slashes('/home/docwhat/.local'),
+          XDG_DATA_HOME = '/home/docwhat/.local',
         } })
-        eq(alter_slashes('/home/docwhat/.local/' .. datadir), fn.stdpath('data'))
+        eq('/home/docwhat/.local/' .. datadir, t.fix_slashes(fn.stdpath('data')))
       end)
 
       it('handles changes during runtime', function()
         clear({ env = {
-          XDG_DATA_HOME = alter_slashes('/home/original'),
+          XDG_DATA_HOME = '/home/original',
         } })
-        eq(alter_slashes('/home/original/' .. datadir), fn.stdpath('data'))
-        command("let $XDG_DATA_HOME='" .. alter_slashes('/home/new') .. "'")
-        eq(alter_slashes('/home/new/' .. datadir), fn.stdpath('data'))
+        eq('/home/original/' .. datadir, t.fix_slashes(fn.stdpath('data')))
+        command("let $XDG_DATA_HOME='/home/new'")
+        eq('/home/new/' .. datadir, t.fix_slashes(fn.stdpath('data')))
       end)
 
       it("doesn't expand $VARIABLES", function()
@@ -1038,14 +1037,14 @@ describe('stdpath()', function()
             VARIABLES = 'this-should-not-happen',
           },
         })
-        eq(alter_slashes('$VARIABLES/' .. datadir), fn.stdpath('data'))
+        eq('$VARIABLES/' .. datadir, t.fix_slashes(fn.stdpath('data')))
       end)
 
       it("doesn't expand ~/", function()
         clear({ env = {
-          XDG_DATA_HOME = alter_slashes('~/frobnitz'),
+          XDG_DATA_HOME = '~/frobnitz',
         } })
-        eq(alter_slashes('~/frobnitz/' .. datadir), fn.stdpath('data'))
+        eq('~/frobnitz/' .. datadir, t.fix_slashes(fn.stdpath('data')))
       end)
     end)
 
@@ -1053,19 +1052,19 @@ describe('stdpath()', function()
       it('knows XDG_STATE_HOME', function()
         clear({
           env = {
-            XDG_STATE_HOME = alter_slashes('/home/docwhat/.local'),
+            XDG_STATE_HOME = '/home/docwhat/.local',
           },
         })
-        eq(alter_slashes('/home/docwhat/.local/' .. statedir), fn.stdpath('state'))
+        eq('/home/docwhat/.local/' .. statedir, t.fix_slashes(fn.stdpath('state')))
       end)
 
       it('handles changes during runtime', function()
         clear({ env = {
-          XDG_STATE_HOME = alter_slashes('/home/original'),
+          XDG_STATE_HOME = '/home/original',
         } })
-        eq(alter_slashes('/home/original/' .. statedir), fn.stdpath('state'))
-        command("let $XDG_STATE_HOME='" .. alter_slashes('/home/new') .. "'")
-        eq(alter_slashes('/home/new/' .. statedir), fn.stdpath('state'))
+        eq('/home/original/' .. statedir, t.fix_slashes(fn.stdpath('state')))
+        command("let $XDG_STATE_HOME='" .. '/home/new' .. "'")
+        eq('/home/new/' .. statedir, t.fix_slashes(fn.stdpath('state')))
       end)
 
       it("doesn't expand $VARIABLES", function()
@@ -1075,14 +1074,14 @@ describe('stdpath()', function()
             VARIABLES = 'this-should-not-happen',
           },
         })
-        eq(alter_slashes('$VARIABLES/' .. statedir), fn.stdpath('state'))
+        eq('$VARIABLES/' .. statedir, t.fix_slashes(fn.stdpath('state')))
       end)
 
       it("doesn't expand ~/", function()
         clear({ env = {
-          XDG_STATE_HOME = alter_slashes('~/frobnitz'),
+          XDG_STATE_HOME = '~/frobnitz',
         } })
-        eq(alter_slashes('~/frobnitz/' .. statedir), fn.stdpath('state'))
+        eq('~/frobnitz/' .. statedir, t.fix_slashes(fn.stdpath('state')))
       end)
     end)
 
@@ -1090,19 +1089,19 @@ describe('stdpath()', function()
       it('knows XDG_CACHE_HOME', function()
         clear({
           env = {
-            XDG_CACHE_HOME = alter_slashes('/home/docwhat/.cache'),
+            XDG_CACHE_HOME = '/home/docwhat/.cache',
           },
         })
-        eq(alter_slashes('/home/docwhat/.cache/nvim'), fn.stdpath('cache'))
+        eq('/home/docwhat/.cache/nvim', t.fix_slashes(fn.stdpath('cache')))
       end)
 
       it('handles changes during runtime', function()
         clear({ env = {
-          XDG_CACHE_HOME = alter_slashes('/home/original'),
+          XDG_CACHE_HOME = '/home/original',
         } })
-        eq(alter_slashes('/home/original/nvim'), fn.stdpath('cache'))
-        command("let $XDG_CACHE_HOME='" .. alter_slashes('/home/new') .. "'")
-        eq(alter_slashes('/home/new/nvim'), fn.stdpath('cache'))
+        eq('/home/original/nvim', t.fix_slashes(fn.stdpath('cache')))
+        command("let $XDG_CACHE_HOME='" .. '/home/new' .. "'")
+        eq('/home/new/nvim', t.fix_slashes(fn.stdpath('cache')))
       end)
 
       it("doesn't expand $VARIABLES", function()
@@ -1112,14 +1111,14 @@ describe('stdpath()', function()
             VARIABLES = 'this-should-not-happen',
           },
         })
-        eq(alter_slashes('$VARIABLES/nvim'), fn.stdpath('cache'))
+        eq('$VARIABLES/nvim', t.fix_slashes(fn.stdpath('cache')))
       end)
 
       it("doesn't expand ~/", function()
         clear({ env = {
-          XDG_CACHE_HOME = alter_slashes('~/frobnitz'),
+          XDG_CACHE_HOME = '~/frobnitz',
         } })
-        eq(alter_slashes('~/frobnitz/nvim'), fn.stdpath('cache'))
+        eq('~/frobnitz/nvim', t.fix_slashes(fn.stdpath('cache')))
       end)
     end)
   end)
@@ -1166,12 +1165,12 @@ describe('stdpath()', function()
       describe(msg, function()
         it('set via system', function()
           set_paths_via_system(env_var_name, paths)
-          eq(expected_paths, fn.stdpath(stdpath_arg))
+          eq(expected_paths, t.fix_slashes(fn.stdpath(stdpath_arg)))
         end)
 
         it('set at runtime', function()
           set_paths_at_runtime(env_var_name, paths)
-          eq(expected_paths, fn.stdpath(stdpath_arg))
+          eq(expected_paths, t.fix_slashes(fn.stdpath(stdpath_arg)))
         end)
       end)
     end
@@ -1182,10 +1181,10 @@ describe('stdpath()', function()
         'config_dirs',
         'XDG_CONFIG_DIRS',
         {
-          alter_slashes('/home/docwhat/.config'),
+          t.fix_slashes('/home/docwhat/.config'),
         },
         {
-          alter_slashes('/home/docwhat/.config/nvim'),
+          t.fix_slashes('/home/docwhat/.config/nvim'),
         }
       )
 
@@ -1194,12 +1193,12 @@ describe('stdpath()', function()
         'config_dirs',
         'XDG_CONFIG_DIRS',
         {
-          alter_slashes('/home/docwhat/.config'),
-          alter_slashes('/etc/config'),
+          t.fix_slashes('/home/docwhat/.config'),
+          t.fix_slashes('/etc/config'),
         },
         {
-          alter_slashes('/home/docwhat/.config/nvim'),
-          alter_slashes('/etc/config/nvim'),
+          t.fix_slashes('/home/docwhat/.config/nvim'),
+          t.fix_slashes('/etc/config/nvim'),
         }
       )
 
@@ -1209,25 +1208,25 @@ describe('stdpath()', function()
         'XDG_CONFIG_DIRS',
         { '$HOME', '$TMP' },
         {
-          alter_slashes('$HOME/nvim'),
-          alter_slashes('$TMP/nvim'),
+          t.fix_slashes('$HOME/nvim'),
+          t.fix_slashes('$TMP/nvim'),
         }
       )
 
       behaves_like_dir_list_env("doesn't expand ~/", 'config_dirs', 'XDG_CONFIG_DIRS', {
-        alter_slashes('~/.oldconfig'),
-        alter_slashes('~/.olderconfig'),
+        t.fix_slashes('~/.oldconfig'),
+        t.fix_slashes('~/.olderconfig'),
       }, {
-        alter_slashes('~/.oldconfig/nvim'),
-        alter_slashes('~/.olderconfig/nvim'),
+        t.fix_slashes('~/.oldconfig/nvim'),
+        t.fix_slashes('~/.olderconfig/nvim'),
       })
     end)
 
     describe('with "data_dirs"', function()
       behaves_like_dir_list_env('knows XDG_DATA_DIRS with one path', 'data_dirs', 'XDG_DATA_DIRS', {
-        alter_slashes('/home/docwhat/.data'),
+        t.fix_slashes('/home/docwhat/.data'),
       }, {
-        alter_slashes('/home/docwhat/.data/nvim'),
+        t.fix_slashes('/home/docwhat/.data/nvim'),
       })
 
       behaves_like_dir_list_env(
@@ -1235,12 +1234,12 @@ describe('stdpath()', function()
         'data_dirs',
         'XDG_DATA_DIRS',
         {
-          alter_slashes('/home/docwhat/.data'),
-          alter_slashes('/etc/local'),
+          t.fix_slashes('/home/docwhat/.data'),
+          t.fix_slashes('/etc/local'),
         },
         {
-          alter_slashes('/home/docwhat/.data/nvim'),
-          alter_slashes('/etc/local/nvim'),
+          t.fix_slashes('/home/docwhat/.data/nvim'),
+          t.fix_slashes('/etc/local/nvim'),
         }
       )
 
@@ -1250,17 +1249,17 @@ describe('stdpath()', function()
         'XDG_DATA_DIRS',
         { '$HOME', '$TMP' },
         {
-          alter_slashes('$HOME/nvim'),
-          alter_slashes('$TMP/nvim'),
+          t.fix_slashes('$HOME/nvim'),
+          t.fix_slashes('$TMP/nvim'),
         }
       )
 
       behaves_like_dir_list_env("doesn't expand ~/", 'data_dirs', 'XDG_DATA_DIRS', {
-        alter_slashes('~/.oldconfig'),
-        alter_slashes('~/.olderconfig'),
+        t.fix_slashes('~/.oldconfig'),
+        t.fix_slashes('~/.olderconfig'),
       }, {
-        alter_slashes('~/.oldconfig/nvim'),
-        alter_slashes('~/.olderconfig/nvim'),
+        t.fix_slashes('~/.oldconfig/nvim'),
+        t.fix_slashes('~/.olderconfig/nvim'),
       })
     end)
   end)
diff --git a/test/functional/terminal/buffer_spec.lua b/test/functional/terminal/buffer_spec.lua
index 767a3dc205..888c4538af 100644
--- a/test/functional/terminal/buffer_spec.lua
+++ b/test/functional/terminal/buffer_spec.lua
@@ -342,7 +342,7 @@ describe(':terminal buffer', function()
     command('wincmd p')
 
     -- cwd will be inserted in a file URI, which cannot contain backs
-    local cwd = fn.getcwd():gsub('\\', '/')
+    local cwd = t.fix_slashes(fn.getcwd())
     local parent = cwd:match('^(.+/)')
     local expected = '\027]7;file://host' .. parent
     api.nvim_chan_send(term, string.format('%s\027\\', expected))
diff --git a/test/functional/testnvim.lua b/test/functional/testnvim.lua
index d74e8055ef..8c8b239cd8 100644
--- a/test/functional/testnvim.lua
+++ b/test/functional/testnvim.lua
@@ -902,26 +902,6 @@ function M.missing_provider(provider)
   assert(false, 'Unknown provider: ' .. provider)
 end
 
---- @param obj string|table
---- @return any
-function M.alter_slashes(obj)
-  if not is_os('win') then
-    return obj
-  end
-  if type(obj) == 'string' then
-    local ret = obj:gsub('/', '\\')
-    return ret
-  elseif type(obj) == 'table' then
-    --- @cast obj table<any,any>
-    local ret = {} --- @type table<any,any>
-    for k, v in pairs(obj) do
-      ret[k] = M.alter_slashes(v)
-    end
-    return ret
-  end
-  assert(false, 'expected string or table of strings, got ' .. type(obj))
-end
-
 local load_factor = 1
 if t.is_ci() then
   -- Compute load factor only once (but outside of any tests).
diff --git a/test/functional/vimscript/fnamemodify_spec.lua b/test/functional/vimscript/fnamemodify_spec.lua
index 51b1e8489a..f2cee9b83e 100644
--- a/test/functional/vimscript/fnamemodify_spec.lua
+++ b/test/functional/vimscript/fnamemodify_spec.lua
@@ -7,11 +7,10 @@ local fnamemodify = n.fn.fnamemodify
 local getcwd = n.fn.getcwd
 local command = n.command
 local write_file = t.write_file
-local alter_slashes = n.alter_slashes
 local is_os = t.is_os
 
 local function eq_slashconvert(expected, got)
-  eq(alter_slashes(expected), alter_slashes(got))
+  eq(t.fix_slashes(expected), t.fix_slashes(got))
 end
 
 describe('fnamemodify()', function()
diff --git a/test/testutil.lua b/test/testutil.lua
index 19e297c503..02f343891d 100644
--- a/test/testutil.lua
+++ b/test/testutil.lua
@@ -42,6 +42,29 @@ function M.isdir(path)
   return stat.type == 'directory'
 end
 
+--- (Only on Windows) Replaces yucky "\\" slashes with delicious "/" slashes in a string, or all
+--- string values in a table (recursively).
+---
+--- @param obj string|table
+--- @return any
+function M.fix_slashes(obj)
+  if not M.is_os('win') then
+    return obj
+  end
+  if type(obj) == 'string' then
+    local ret = obj:gsub('\\', '/')
+    return ret
+  elseif type(obj) == 'table' then
+    --- @cast obj table<any,any>
+    local ret = {} --- @type table<any,any>
+    for k, v in pairs(obj) do
+      ret[k] = M.fix_slashes(v)
+    end
+    return ret
+  end
+  assert(false, 'expected string or table of strings, got ' .. type(obj))
+end
+
 --- @param ... string|string[]
 --- @return string
 function M.argss_to_cmd(...)