diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..a36246a
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,28 @@
+name: default
+
+on: [push, pull_request]
+
+jobs:
+  run_tests:
+    name: unit tests
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]
+        neovim_version: ['v0.8.3', 'v0.9.5', 'v0.10.2', 'nightly']
+        include:
+        - os: macos-latest
+          neovim_version: v0.10.1
+        - os: windows-latest
+          neovim_version: v0.10.1
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup neovim
+        uses: rhysd/action-setup-vim@v1
+        with:
+          neovim: true
+          version: ${{ matrix.neovim_version }}
+      - name: Run tests
+        timeout-minutes: 3
+        run: make test
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..4c0f4dc
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,11 @@
+test: deps/mini.nvim
+	nvim --headless --noplugin -u ./scripts/minimal_init.lua -c "lua MiniTest.run()"
+
+# Run test from file at `$FILE` environment variable
+test_file: deps/mini.nvim
+	nvim --headless --noplugin -u ./scripts/minimal_init.lua -c "lua MiniTest.run_file('$(FILE)')"
+
+# Download 'mini.nvim' to use its 'mini.test' testing module
+deps/mini.nvim:
+	@mkdir -p deps
+	git clone --filter=blob:none https://github.com/echasnovski/mini.nvim $@
diff --git a/lua/scratch/utils.lua b/lua/scratch/utils.lua
index 6546d87..4c21e7e 100644
--- a/lua/scratch/utils.lua
+++ b/lua/scratch/utils.lua
@@ -77,17 +77,29 @@ local table_length = function(T)
 end
 
 ---@return string[]
-local function getSelectedText()
-  local _, csrow, cscol, _ = unpack(vim.fn.getpos("'<"))
-  local _, cerow, cecol, _ = unpack(vim.fn.getpos("'>"))
-
-  local lines = vim.fn.getline(csrow, cerow)
-  local n = table_length(lines)
-  if n <= 0 then
-    return {}
+local function getSelectedText(mark, selection_mode)
+  local pos1 = vim.fn.getpos("v")
+  local pos2 = vim.fn.getpos(mark)
+  local lines = {}
+  local start_row, start_col, end_row, end_col = pos1[2], pos1[3], pos2[2], pos2[3]
+  local text = vim.api.nvim_buf_get_lines(0, start_row - 1, end_row, true)
+  end_row = end_row - start_row + 1
+  start_row = 1
+  if selection_mode == "v" then
+    table.insert(lines, text[1]:sub(start_col))
+    for i = start_row + 1, end_row do
+      table.insert(lines, text[i])
+    end
+    lines[end_row] = lines[end_row]:sub(1, end_col)
+  elseif selection_mode == "V" then
+    for i = start_row, end_row do
+      table.insert(lines, text[i])
+    end
+  elseif selection_mode == vim.api.nvim_replace_termcodes("<C-V>", true, true, true) then
+    for i = start_row, end_row do
+      table.insert(lines, text[i]:sub(start_col, end_col))
+    end
   end
-  lines[n] = string.sub(lines[n], 1, cecol)
-  lines[1] = string.sub(lines[1], cscol)
   return lines
 end
 
diff --git a/plugin/scratch_plugin.lua b/plugin/scratch_plugin.lua
index b79c4c4..eacd90a 100644
--- a/plugin/scratch_plugin.lua
+++ b/plugin/scratch_plugin.lua
@@ -16,11 +16,14 @@ local scratch_main = require("scratch")
 scratch_main.setup()
 
 vim.api.nvim_create_user_command("Scratch", function(args)
-  if args.range > 0 then
-    scratch_api.scratch({ content = utils.getSelectedText() })
-  else
-    scratch_api.scratch()
+  local mode = vim.api.nvim_get_mode().mode
+  local opts
+  if mode ~= "n" then
+    opts = { content = utils.getSelectedText(".", mode) }
+  elseif args.range > 0 then
+    opts = { content = vim.api.nvim_buf_get_lines(0, args.line1 - 1, args.line2, true) }
   end
+  scratch_api.scratch(opts)
 end, { range = true })
 
 vim.api.nvim_create_user_command("ScratchOpen", scratch_api.openScratch, {})
diff --git a/scripts/minimal_init.lua b/scripts/minimal_init.lua
new file mode 100644
index 0000000..7af7ee3
--- /dev/null
+++ b/scripts/minimal_init.lua
@@ -0,0 +1,12 @@
+-- Add current directory to 'runtimepath' to be able to use 'lua' files
+vim.cmd([[let &rtp.=','.getcwd()]])
+
+-- Set up 'mini.test' only when calling headless Neovim (like with `make test`)
+if #vim.api.nvim_list_uis() == 0 then
+  -- Add 'mini.nvim' to 'runtimepath' to be able to use 'mini.test'
+  -- Assumed that 'mini.nvim' is stored in 'deps/mini.nvim'
+  vim.cmd("set rtp+=deps/mini.nvim")
+
+  -- Set up 'mini.test'
+  require("mini.test").setup()
+end
diff --git a/tests/test_plugin.lua b/tests/test_plugin.lua
new file mode 100644
index 0000000..427e070
--- /dev/null
+++ b/tests/test_plugin.lua
@@ -0,0 +1,135 @@
+local child = MiniTest.new_child_neovim()
+local new_set = MiniTest.new_set
+
+local function mock()
+  local mock_api = {}
+  mock_api.scratch = function(opts)
+    _G.scratch_opts = opts
+  end
+  mock_api.openScratch = function()
+    print("TODO")
+  end
+  mock_api.fzfScratch = mock_api.openScratch
+  mock_api.scratchWithName = mock_api.openScratch
+
+  package.loaded["scratch.api"] = mock_api
+  vim.g.loaded_scratch = 0
+  dofile("plugin/scratch_plugin.lua")
+end
+local select_wise = function(coord, selection_mode)
+  local vim = child
+  local start_row, start_col, end_row, end_col = coord[1], coord[2], coord[3], coord[4]
+  local mode = vim.api.nvim_get_mode()
+  if mode.mode ~= "n" then
+    local esc = vim.api.nvim_replace_termcodes("<ESC>", true, true, true)
+    vim.api.nvim_cmd({ cmd = "normal", bang = true, args = { esc } }, {})
+    vim.api.nvim_cmd({ cmd = "normal", bang = true, args = { esc } }, {})
+  end
+  selection_mode = vim.api.nvim_replace_termcodes(selection_mode, true, true, true)
+  vim.api.nvim_cmd({ cmd = "normal", bang = true, args = { selection_mode } }, {})
+
+  vim.api.nvim_win_set_cursor(0, { start_row, start_col - 1 })
+  vim.cmd("normal! o")
+  vim.api.nvim_win_set_cursor(0, { end_row, end_col - 1 })
+end
+
+local function table_select(text, coord, selection_mode)
+  local lines = {}
+  local start_row, start_col, end_row, end_col = coord[1], coord[2], coord[3], coord[4]
+  if selection_mode == "v" then
+    table.insert(lines, text[start_row]:sub(start_col))
+    for i = start_row + 1, end_row do
+      table.insert(lines, text[i])
+    end
+    local ind = end_row - start_row + 1
+    lines[ind] = lines[ind]:sub(1, end_col)
+  elseif selection_mode == "V" then
+    for i = start_row, end_row do
+      table.insert(lines, text[i])
+    end
+  elseif selection_mode == vim.api.nvim_replace_termcodes("<C-V>", true, true, true) then
+    for i = start_row, end_row do
+      table.insert(lines, text[i]:sub(start_col, end_col))
+    end
+  end
+  return lines
+end
+local T = new_set()
+T["Scratch"] = new_set({
+  hooks = {
+    pre_once = function()
+      child.restart({ "-u", "scripts/minimal_init.lua" })
+      child.lua_func(mock)
+    end,
+    post_once = child.stop,
+  },
+})
+local BUFFER_TEXT = {
+  "some",
+  "text here will be",
+  "inserted",
+  "now",
+}
+T["Scratch"]["select_branch"] = new_set({
+  parametrize = { { "v" }, { "V" }, { vim.api.nvim_replace_termcodes("<C-V>", true, true, true) } },
+})
+T["Scratch"]["select_branch"]["parameter"] = new_set({
+  parametrize = {
+    {
+      { 1, 1, 1, 4 },
+    },
+    {
+      { 1, 2, 1, 4 },
+    },
+    {
+      { 2, 1, 3, 4 },
+    },
+    {
+      { 1, 1, 2, 2 },
+    },
+    {
+      { 1, 1, 1, 1 },
+    },
+    {
+      { 1, 1, 4, 4 },
+    },
+  },
+})
+T["Scratch"]["select_branch"]["parameter"]["some_text"] = function(selection_mode, coord)
+  child.api.nvim_buf_set_lines(0, 0, -1, false, BUFFER_TEXT)
+  child.api.nvim_set_keymap("v", "  ", ":Scratch<CR>", {})
+  select_wise(coord, selection_mode)
+  MiniTest.add_note("|1>" .. vim.inspect(child.api.nvim_get_mode()))
+  MiniTest.add_note(
+    "|2>"
+      .. vim.inspect(
+        child.lua_get(
+          [[require("scratch.utils").getSelectedText(".", vim.api.nvim_get_mode().mode)]]
+        )
+      )
+  )
+  child.type_keys("  ")
+  MiniTest.expect.equality(
+    table_select(BUFFER_TEXT, coord, selection_mode),
+    child.lua_get("_G.scratch_opts").content
+  )
+end
+T["Scratch"]["range_branch"] = new_set()
+T["Scratch"]["range_branch"]["lines"] = function()
+  child.api.nvim_buf_set_lines(0, 0, -1, false, BUFFER_TEXT)
+  child.type_keys(":1,2Scratch<CR>")
+  MiniTest.expect.equality(
+    table_select(BUFFER_TEXT, { 1, 1, 2, 2 }, "V"),
+    child.lua_get("_G.scratch_opts").content
+  )
+end
+T["Scratch"]["range_branch"]["selection"] = function()
+  child.api.nvim_buf_set_lines(0, 0, -1, false, BUFFER_TEXT)
+  select_wise({ 1, 1, 3, 3 }, "V")
+  child.type_keys(":", "Scratch<CR>")
+  MiniTest.expect.equality(
+    table_select(BUFFER_TEXT, { 1, 1, 3, 2 }, "V"),
+    child.lua_get("_G.scratch_opts").content
+  )
+end
+return T
diff --git a/tests/test_select.lua b/tests/test_select.lua
new file mode 100644
index 0000000..15d9dd6
--- /dev/null
+++ b/tests/test_select.lua
@@ -0,0 +1,168 @@
+local child = MiniTest.new_child_neovim()
+local getSelectedText
+local function table_select(text, coord, selection_mode)
+  local lines = {}
+  local start_row, start_col, end_row, end_col = coord[1], coord[2], coord[3], coord[4]
+  if selection_mode == "v" then
+    table.insert(lines, text[start_row]:sub(start_col))
+    for i = start_row + 1, end_row do
+      table.insert(lines, text[i])
+    end
+    local ind = end_row - start_row + 1
+    lines[ind] = lines[ind]:sub(1, end_col)
+  elseif selection_mode == "V" then
+    for i = start_row, end_row do
+      table.insert(lines, text[i])
+    end
+  elseif selection_mode == vim.api.nvim_replace_termcodes("<C-V>", true, true, true) then
+    for i = start_row, end_row do
+      table.insert(lines, text[i]:sub(start_col, end_col))
+    end
+  end
+  return lines
+end
+local select_wise = function(coord, selection_mode)
+  local vim = child
+  local start_row, start_col, end_row, end_col = coord[1], coord[2], coord[3], coord[4]
+  local mode = vim.api.nvim_get_mode()
+  if mode.mode ~= "n" then
+    local esc = vim.api.nvim_replace_termcodes("<ESC>", true, true, true)
+    vim.api.nvim_cmd({ cmd = "normal", bang = true, args = { esc } }, {})
+    vim.api.nvim_cmd({ cmd = "normal", bang = true, args = { esc } }, {})
+  end
+  selection_mode = vim.api.nvim_replace_termcodes(selection_mode, true, true, true)
+  vim.api.nvim_cmd({ cmd = "normal", bang = true, args = { selection_mode } }, {})
+
+  vim.api.nvim_win_set_cursor(0, { start_row, start_col - 1 })
+  vim.cmd("normal! o")
+  vim.api.nvim_win_set_cursor(0, { end_row, end_col - 1 })
+end
+
+-- local function old_real(mark, mode)
+--   local _, csrow, cscol, _ = unpack(vim.fn.getpos("'<"))
+--   local _, cerow, cecol, _ = unpack(vim.fn.getpos("'>"))
+--
+--   local lines = vim.fn.getline(csrow, cerow)
+--   local n = #lines
+--   if n <= 0 then
+--     return {}
+--   end
+--   lines[n] = string.sub(lines[n], 1, cecol)
+--   lines[1] = string.sub(lines[1], cscol)
+--   return lines
+-- end
+
+local new_set = MiniTest.new_set
+local T = new_set({
+  parametrize = { { "v" }, { "V" }, { vim.api.nvim_replace_termcodes("<C-V>", true, true, true) } },
+})
+T["param"] = new_set({
+  parametrize = {
+    {
+      { 1, 1, 1, 4 },
+    },
+    {
+      { 1, 2, 1, 4 },
+    },
+    {
+      { 2, 1, 3, 4 },
+    },
+    {
+      { 1, 1, 2, 2 },
+    },
+    {
+      { 1, 1, 1, 1 },
+    },
+    {
+      { 1, 1, 4, 4 },
+    },
+  },
+})
+local BUFFER_TEXT = {
+  "some",
+  "text here will be",
+  "inserted",
+  "now",
+}
+-- T["param"]["old"] = new_set({
+--   hooks = {
+--     pre_case = function()
+--       child.restart({ "-u", "scripts/minimal_init.lua" })
+--       child.api.nvim_buf_set_lines(0, 0, -1, false, BUFFER_TEXT)
+--     end,
+--     post_case = function()
+--       child.stop()
+--     end,
+--   },
+-- })
+T["param"]["new"] = new_set({
+  hooks = {
+    pre_case = function()
+      child.restart({ "-u", "scripts/minimal_init.lua" })
+      child.api.nvim_buf_set_lines(0, 0, -1, false, BUFFER_TEXT)
+      getSelectedText = require("scratch.utils").getSelectedText
+    end,
+    post_case = function()
+      child.stop()
+    end,
+  },
+  n_retry = 2,
+})
+-- T["param"]["old"]["not_workd"] = function(selection_mode, coord)
+--   select_wise(coord, selection_mode)
+--   MiniTest.expect.no_equality(
+--     table_select(BUFFER_TEXT, coord, selection_mode),
+--     child.lua_func(old_real)
+--   )
+-- end
+T["param"]["new"]["workd"] = function(selection_mode, coord)
+  select_wise(coord, selection_mode)
+  MiniTest.expect.equality(
+    table_select(BUFFER_TEXT, coord, selection_mode),
+    child.lua_func(getSelectedText, ".", selection_mode)
+  )
+end
+-- T["param"]["old"]["at_command"] = function(selection_mode, coord)
+--   select_wise(coord, selection_mode)
+--   child.type_keys(":")
+--   MiniTest.expect.equality(
+--     table_select(BUFFER_TEXT, coord, selection_mode),
+--     child.lua_func(old_real)
+--   )
+-- end
+T["param"]["new"]["at_command"] = function(selection_mode, coord)
+  select_wise(coord, selection_mode)
+  child.type_keys(":")
+  MiniTest.add_note("|1>--- " .. vim.inspect(child.fn.getpos("'>")))
+  MiniTest.add_note("|2>--- " .. vim.inspect(child.fn.getpos(".")))
+  MiniTest.expect.equality(
+    table_select(BUFFER_TEXT, coord, selection_mode),
+    child.lua_func(getSelectedText, "'>", selection_mode)
+  )
+end
+T["new"] = new_set({
+  hooks = {
+    pre_case = function()
+      child.restart({ "-u", "scripts/minimal_init.lua" })
+      child.api.nvim_buf_set_lines(0, 0, -1, false, {})
+      getSelectedText = require("scratch.utils").getSelectedText
+    end,
+    post_case = function()
+      child.stop()
+    end,
+  },
+  parametrize = { { { 1, 1, 1, 1 } } },
+})
+T["new"]["empty_file"] = function(selection_mode, coord)
+  select_wise(coord, selection_mode)
+  local pos1 = child.fn.getpos("v")
+  local pos2 = child.fn.getpos(".")
+  MiniTest.add_note("|1>--- " .. vim.inspect(pos1))
+  MiniTest.add_note("|2>--- " .. vim.inspect(pos2))
+  MiniTest.expect.equality(
+    table_select({ "" }, coord, selection_mode),
+    child.lua_func(getSelectedText, ".", selection_mode)
+  )
+end
+
+return T