Added unittest + basic python and lua unittests (#174)

---------

Co-authored-by: Danymat <d.danymat@gmail.com>

tests/utils/specs.lua

@@ -0,0 +1,47 @@
+local textmate = require("tests.utils.textmate")
+local neogen = require("neogen")
+
+local M = {}
+
+--- Make a docstring for given language and return the `neogen` result.
+---@param source string Pseudo-source-code to call. It contains `"|cursor|"` which is the expected user position.
+---@param filetype string Buffer filetype.
+---@param neogen_opts table? Custom Neogen opts passed during generate command.
+---@return string? # The same source code, after calling neogen.
+function M.make_docstring(source, filetype, neogen_opts)
+    local result = textmate.extract_cursors(source)
+
+    if not result then
+        vim.notify(
+            string.format("Source\n\n%s\n\nwas not parsable. Does it have a |cursor| defined?", source),
+            vim.log.levels.ERROR
+        )
+
+        return nil
+    end
+
+    local cursors, code = unpack(result)
+
+    local buffer = vim.api.nvim_create_buf(true, true)
+    vim.bo[buffer].filetype = filetype
+    vim.cmd.buffer(buffer)
+    local window = vim.fn.win_getid() -- We just created the buffer so the current window works
+
+    local strict_indexing = false
+    vim.api.nvim_buf_set_lines(buffer, 0, -1, strict_indexing, vim.fn.split(code, "\n"))
+
+    -- IMPORTANT: Because we are adding docstrings in the buffer, we must start
+    -- from the bottom docstring up. Otherwise the row/column positions of the
+    -- next `cursor` in `cursors` will be out of date.
+    for index = #cursors, 1, -1 do
+        local cursor = cursors[index]
+        vim.api.nvim_win_set_cursor(window, cursor)
+
+        neogen_opts = vim.tbl_deep_extend("force", { snippet_engine = "nvim" }, neogen_opts or {})
+        neogen.generate(neogen_opts)
+    end
+
+    return table.concat(vim.api.nvim_buf_get_lines(buffer, 0, -1, strict_indexing), "\n")
+end
+
+return M

tests/utils/textmate.lua

@@ -0,0 +1,65 @@
+--- A file to make dealing with text in Lua a little easier.
+---
+--- @module 'tests.textmate'
+
+local _CURSOR_MARKER = "|cursor|"
+
+local M = {}
+
+---@class Cursor
+---    A fake position in-space where a user's cursor is meant to be.
+---@field [1] number
+---    A 1-or-more value indicating the buffer line value.
+---@field [2] number
+---    A 1-or-more value indicating the buffer column value.
+
+--- Find all lines marked with `"|cursor|"` and return their row / column positions.
+---
+---@param source string Pseudo-Python source-code to call. It contains `"|cursor|"` which is the expected user position.
+---@return Cursor[] # The row and column cursor position in `source`.
+---@return string # The same source code but with `"|cursor|"` stripped out.
+function M.extract_cursors(source)
+  local index = 1
+  local count = #source
+  local cursors = {}
+  local cursor_marker_offset = #_CURSOR_MARKER - 1
+  local code = ""
+
+  local current_row = 1
+  local current_column = 1
+
+  while index <= count do
+    local character = source:sub(index, index)
+
+    if character == "\n" then
+      current_row = current_row + 1
+      current_column = 1
+    else
+      current_column = current_column + 1
+    end
+
+    if character == "|" then
+      if source:sub(index, index + cursor_marker_offset) == _CURSOR_MARKER then
+        index = index + cursor_marker_offset
+        table.insert(cursors, { current_row, current_column })
+      else
+        code = code .. character
+      end
+    else
+      code = code .. character
+    end
+
+    index = index + 1
+  end
+
+  if index <= count then
+    -- If this happens, is because the while loop called `break` early
+    -- This is very likely so we add the last character(s) to the output
+    local remainder = source:sub(index, #source)
+    code = code .. remainder
+  end
+
+  return { cursors, code }
+end
+
+return M