test(textobj): add tests for textobject

Add unit tests for the textobject module in csvview. These tests
cover various scenarios including selecting fields with and without
delimiters, handling comments, and empty lines.

tests/textobject_spec.lua

@@ -0,0 +1,83 @@
+---@diagnostic disable: await-in-sync
+local config = require("csvview.config")
+local csvview = require("csvview")
+local textobject = require("csvview.textobject")
+
+---@type CsvView.Options
+local opts = { parser = { comments = { "#" } } }
+
+local lines = {
+  "Index,ID,Name,Email,Birthday",
+  "1,XUMMW7737A,Jane Davis,jane.williams@example.org,1964-03-22",
+  "# this is a comment",
+  "",
+}
+
+---@class CsvView.TextObjectCase
+---@field name string
+---@field cursor { row: integer, col: integer } 1-based row and 0-based column
+---@field opts { include_delimiter: boolean }
+---@field expected string
+
+---@type CsvView.TextObjectCase[]
+local cases = {
+  {
+    name = "selects the current field without delimiter",
+    cursor = { row = 2, col = string.find(lines[2], "M") }, ---@diagnostic disable-line
+    opts = { include_delimiter = false },
+    expected = "XUMMW7737A",
+  },
+  {
+    name = "selects the current field with delimiter. The cursor is first column",
+    cursor = { row = 2, col = 0 },
+    opts = { include_delimiter = true },
+    expected = "1,",
+  },
+  {
+    name = "selects the current field with delimiter. The cursor is last column",
+    cursor = { row = 2, col = string.find(lines[2], "4") }, ---@diagnostic disable-line
+    opts = { include_delimiter = true },
+    expected = ",1964-03-22",
+  },
+  {
+    name = "select nothing if the cursor is on a comment line",
+    cursor = { row = 3, col = 0 },
+    opts = { include_delimiter = false },
+    expected = "",
+  },
+  {
+    name = "select nothing if the cursor is on an empty line",
+    cursor = { row = 4, col = 0 },
+    opts = { include_delimiter = false },
+    expected = "",
+  },
+}
+
+describe("csvview.textobject", function()
+  before_each(function()
+    config.setup()
+    csvview.setup()
+  end)
+
+  for _, case in ipairs(cases) do
+    it(case.name, function()
+      local bufnr = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+      vim.api.nvim_win_set_buf(0, bufnr)
+
+      csvview.enable(bufnr, opts)
+
+      -- Move cursor to the specified field
+      vim.api.nvim_win_set_cursor(0, { case.cursor.row, case.cursor.col })
+      textobject.field(bufnr, case.opts)
+
+      -- Clear the register
+      vim.fn.setreg("0", "")
+
+      -- Copy the selected text
+      vim.cmd("normal! y")
+      local selected = vim.fn.getreg("0")
+      assert.are.same(case.expected, selected)
+    end)
+  end
+end)