diff --git a/lua/waitevent/vendor/assertlib/asserter.lua b/lua/waitevent/vendor/assertlib/asserter.lua
index 4268578..49f1e9d 100644
--- a/lua/waitevent/vendor/assertlib/asserter.lua
+++ b/lua/waitevent/vendor/assertlib/asserter.lua
@@ -6,18 +6,29 @@ function M.new(name, attributes)
     attributes = { attributes, "table" },
   })
   attributes.get_actual = attributes.get_actual or function() end
+  attributes.get_actual_args = attributes.get_actual_args
+    or function(args)
+      return { unpack(args, 1, #args - 1) }
+    end
   attributes.get_expected = attributes.get_expected or function(...)
     return ...
   end
+  attributes.get_expected_args = attributes.get_expected_args or function(args)
+    return { args[#args] }
+  end
   return {
     name = name,
     get_result = function(args)
-      local expected = attributes.get_expected(args[#args])
-      local actual = attributes.get_actual(unpack(args, 1, #args - 1))
+      local expected_args = attributes.get_expected_args(args)
+      local expected = attributes.get_expected(unpack(expected_args))
+      local actual_args = attributes.get_actual_args(args)
+      local actual = attributes.get_actual(unpack(actual_args))
       return {
         name = name,
         expected = expected,
+        expected_args = expected_args,
         actual = actual,
+        actual_args = actual_args,
       }
     end,
     is_ok = attributes.is_ok or function(result)
diff --git a/lua/waitevent/vendor/assertlib/function/buffer.lua b/lua/waitevent/vendor/assertlib/function/buffer.lua
index 7107b9f..6c50359 100644
--- a/lua/waitevent/vendor/assertlib/function/buffer.lua
+++ b/lua/waitevent/vendor/assertlib/function/buffer.lua
@@ -22,21 +22,29 @@ function M.buffer_number()
 end
 
 M.exists_pattern = {
+  get_expected_args = function(args)
+    return args
+  end,
   get_expected = function(pattern)
     return pattern:gsub("\n", "\\n")
   end,
   is_ok = function(result)
-    return vim.fn.search(result.expected, "n") ~= 0
+    local bufnr = result.expected_args[2] or 0
+    return vim.api.nvim_buf_call(bufnr, function()
+      return vim.fn.search(result.expected, "n") ~= 0
+    end)
   end,
   positive_message = function(result)
-    local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
+    local bufnr = result.expected_args[2] or 0
+    local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
     local content = table.concat(lines, "\n")
     return ([[`%s` not found
 Actual lines:
 %s]]):format(result.expected, content)
   end,
   negative_message = function(result)
-    local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
+    local bufnr = result.expected_args[2] or 0
+    local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
     local content = table.concat(lines, "\n")
     return ([[`%s` found
 Actual lines:
diff --git a/lua/waitevent/vendor/misclib/test/data_dir.lua b/lua/waitevent/vendor/misclib/test/data_dir.lua
index be401ad..d298d98 100644
--- a/lua/waitevent/vendor/misclib/test/data_dir.lua
+++ b/lua/waitevent/vendor/misclib/test/data_dir.lua
@@ -4,9 +4,9 @@ M.__index = M
 function M.setup(root_path, opts)
   opts = opts or {}
   local base_dir = opts.base_dir or "test_data/"
-  local base_path = root_path .. "/" .. base_dir
+  local base_path = vim.fs.joinpath(root_path, base_dir)
   local relative_path = base_dir .. math.random(1, 2 ^ 30) .. "/"
-  local full_path = root_path .. "/" .. relative_path
+  local full_path = vim.fs.joinpath(root_path, relative_path)
   local tbl = {
     relative_path = relative_path,
     full_path = full_path,
@@ -22,7 +22,7 @@ end
 function M.create_file(self, path, content)
   self:create_dir(vim.fs.dirname(path))
 
-  local file_path = self.full_path .. path
+  local file_path = vim.fs.joinpath(self.full_path, path)
   local f = io.open(file_path, "w")
   if not f then
     error("cannot open: " .. file_path)
@@ -36,13 +36,14 @@ function M.create_file(self, path, content)
 end
 
 function M.create_dir(self, path)
-  local dir_path = self.full_path .. path
+  local dir_path = vim.fs.joinpath(self.full_path, path)
   vim.fn.mkdir(dir_path, "p")
   return dir_path
 end
 
 function M.cd(self, path)
-  vim.api.nvim_set_current_dir(self.full_path .. path)
+  local dir_path = vim.fs.joinpath(self.full_path, path)
+  vim.api.nvim_set_current_dir(dir_path)
 end
 
 local delete = function(target_path)
@@ -53,7 +54,7 @@ local delete = function(target_path)
 end
 
 function M.delete(self, path)
-  local target_path = self.full_path .. path
+  local target_path = vim.fs.joinpath(self.full_path, path)
   delete(target_path)
 end