diff --git a/.bin/dotfiles-test b/.bin/dotfiles-test
new file mode 100755
index 0000000..57dba64
--- /dev/null
+++ b/.bin/dotfiles-test
@@ -0,0 +1,247 @@
+#!/bin/zsh
+
+# Test this dotfiles repo without requiring project-local package manifests or a
+# non-bare checkout in the real home directory.
+#
+# Default mode runs in a disposable normal clone so package-manager state,
+# Neovim plugin bootstrap, and other temporary files stay out of the author's
+# actual `$HOME`. `--here` runs the same checks in the current checkout, which
+# is useful for CI and for explicit local debugging.
+#
+# Coverage:
+# - Markdown formatting with Prettier
+# - Lua formatting and lint for the tracked Neovim config
+# - Zsh syntax for the shell entrypoints
+# - A headless Neovim startup smoke test with isolated XDG state
+#
+# The script installs the Node-backed Markdown formatter into a temporary
+# directory on each run instead of relying on a tracked `package.json` or
+# `node_modules`.
+
+set -euo pipefail
+
+script_dir=${0:A:h}
+repo_root=${script_dir:h}
+run_here=0
+assume_yes=0
+apply_fixes=0
+keep_clone=${DOTFILES_CI_KEEP_CLONE:-0}
+
+usage() {
+  cat <<'EOF'
+Usage:
+  dotfiles-test [--here] [--fix] [--yes]
+
+Without arguments, run the checks in a disposable normal clone.
+
+Options:
+  --here        Run in the current checkout instead of a temp clone.
+  --fix         Apply fixes where supported before running the remaining checks.
+  -y, --yes     Skip the confirmation prompt for --here.
+  -h, --help    Show this help.
+EOF
+}
+
+while (( $# > 0 )); do
+  case "$1" in
+    --here)
+      run_here=1
+      ;;
+    --fix)
+      apply_fixes=1
+      ;;
+    -y|--yes)
+      assume_yes=1
+      ;;
+    -h|--help)
+      usage
+      exit 0
+      ;;
+    *)
+      print -u2 "dotfiles-test: unknown argument: $1"
+      usage >&2
+      exit 2
+      ;;
+  esac
+  shift
+done
+
+if [[ -d "$repo_root/.dotfiles" ]]; then
+  git_cmd=(git --git-dir="$repo_root/.dotfiles" --work-tree="$repo_root")
+  clone_source=$repo_root/.dotfiles
+elif git -C "$repo_root" rev-parse --show-toplevel >/dev/null 2>&1; then
+  git_cmd=(git -C "$repo_root")
+  clone_source=$repo_root
+else
+  print -u2 "dotfiles-test: could not find the dotfiles repository from $repo_root"
+  exit 1
+fi
+
+cd "$repo_root"
+
+require_cmd() {
+  local cmd=$1
+  local help=${2:-}
+
+  if command -v "$cmd" >/dev/null 2>&1; then
+    return 0
+  fi
+
+  print -u2 "dotfiles-test: missing required command: $cmd"
+  if [[ -n "$help" ]]; then
+    print -u2 "dotfiles-test: $help"
+  fi
+  exit 127
+}
+
+run_checks_here() {
+  local work_root=$1
+
+  cd "$work_root"
+
+  require_cmd git
+  require_cmd node "Install Node 22 via mise, for example: mise use -g node@22"
+  require_cmd npm "Install Node 22 via mise, for example: mise use -g node@22"
+  require_cmd nvim "Install Neovim, for example: brew install neovim"
+  require_cmd stylua "Install Stylua, for example: brew install stylua"
+  require_cmd luacheck "Install Luacheck, for example: brew install luacheck"
+  require_cmd zsh "Install zsh, for example: brew install zsh"
+
+  local tmp_root
+  tmp_root=$(mktemp -d "${TMPDIR:-/tmp}/dotfiles-test.XXXXXX")
+
+  local tracked_md=()
+  local markdown_path
+  for markdown_path in "${(@0)$("${git_cmd[@]}" ls-files -z -- '*.md')}"; do
+    if [[ -n "$markdown_path" && ! -L "$work_root/$markdown_path" ]]; then
+      tracked_md+=("$markdown_path")
+    fi
+  done
+
+  if (( ${#tracked_md[@]} > 0 )); then
+    npm install \
+      --prefix "$tmp_root/npm-tools" \
+      --no-package-lock \
+      --no-save \
+      prettier@3 >/dev/null
+
+    if (( apply_fixes == 1 )); then
+      "$tmp_root/npm-tools/node_modules/.bin/prettier" --list-different --write -- "${tracked_md[@]}"
+    else
+      "$tmp_root/npm-tools/node_modules/.bin/prettier" --list-different -- "${tracked_md[@]}"
+    fi
+  fi
+
+  if (( apply_fixes == 1 )); then
+    stylua .vim/init.lua .vim/lua
+  else
+    stylua --check .vim/init.lua .vim/lua
+  fi
+  luacheck --config .vim/.luacheckrc .vim/init.lua .vim/lua
+  zsh -n .zshenv .zshrc
+
+  mkdir -p \
+    "$tmp_root/xdg-cache" \
+    "$tmp_root/xdg-data" \
+    "$tmp_root/xdg-state"
+
+  local nvim_log="$tmp_root/nvim.log"
+  if ! env \
+    HOME="$work_root" \
+    XDG_CACHE_HOME="$tmp_root/xdg-cache" \
+    XDG_DATA_HOME="$tmp_root/xdg-data" \
+    XDG_STATE_HOME="$tmp_root/xdg-state" \
+    nvim --headless "+Lazy! restore" "+qa" >"$nvim_log" 2>&1; then
+    cat "$nvim_log"
+    rm -rf "$tmp_root"
+    exit 1
+  fi
+
+  rm -rf "$tmp_root"
+}
+
+run_checks_in_temp_clone() {
+  require_cmd git
+  require_cmd rsync "Install rsync, for example: brew install rsync"
+
+  local tmp_root
+  tmp_root=$(mktemp -d "${TMPDIR:-/tmp}/dotfiles-test-clone.XXXXXX")
+
+  cleanup_clone() {
+    if [[ "$keep_clone" == "1" ]]; then
+      print "dotfiles-test: kept temp clone at $tmp_root/repo"
+      return 0
+    fi
+
+    rm -rf "$tmp_root"
+  }
+
+  git clone "$clone_source" "$tmp_root/repo" >/dev/null
+
+  local overlay_files=("${(@0)$("${git_cmd[@]}" ls-files -z)}")
+  overlay_files=("${(@)overlay_files:#}")
+  overlay_files=("${(@)overlay_files:#(#m)(?)}")
+  local extra_dir
+  for extra_dir in .bin .github; do
+    if [[ ! -d "$repo_root/$extra_dir" ]]; then
+      continue
+    fi
+
+    local extra_files=("${(@0)$("${git_cmd[@]}" ls-files -z --others --exclude-standard -- "$extra_dir")}")
+    overlay_files+=("${extra_files[@]}")
+  done
+
+  local existing_overlay_files=()
+  local overlay_file
+  for overlay_file in "${overlay_files[@]}"; do
+    if [[ -e "$repo_root/$overlay_file" || -L "$repo_root/$overlay_file" ]]; then
+      existing_overlay_files+=("$overlay_file")
+    fi
+  done
+
+  if (( ${#existing_overlay_files[@]} > 0 )); then
+    rsync -a --files-from=<(printf '%s\0' "${existing_overlay_files[@]}") --from0 "$repo_root"/ "$tmp_root/repo"/
+  fi
+
+  local deleted_files=("${(@0)$("${git_cmd[@]}" ls-files -z --deleted)}")
+  if (( ${#deleted_files[@]} > 0 )); then
+    (cd "$tmp_root/repo" && rm -f -- "${deleted_files[@]}")
+  fi
+
+  local nested_args=(--here --yes)
+  if (( apply_fixes == 1 )); then
+    nested_args+=(--fix)
+  fi
+
+  (cd "$tmp_root/repo" && ./.bin/dotfiles-test "${nested_args[@]}")
+  cleanup_clone
+}
+
+confirm_here_run() {
+  if (( assume_yes == 1 )); then
+    return 0
+  fi
+
+  local prompt="dotfiles-test: run checks in the current checkout and allow temporary files under this checkout? [y/N] "
+  local reply
+
+  if [[ -t 0 ]]; then
+    read -r "?$prompt" reply
+  else
+    print -u2 "$prompt"
+    read -r reply || return 1
+  fi
+
+  [[ "$reply" == [Yy] || "$reply" == [Yy][Ee][Ss] ]]
+}
+
+if (( run_here == 1 )); then
+  if ! confirm_here_run; then
+    print -u2 "dotfiles-test: aborted"
+    exit 1
+  fi
+
+  run_checks_here "$repo_root"
+else
+  run_checks_in_temp_clone
+fi
diff --git a/.docs/GIT.md b/.docs/GIT.md
index 41c543b..7f9e5ef 100644
--- a/.docs/GIT.md
+++ b/.docs/GIT.md
@@ -64,15 +64,15 @@ Get latest
 </td>
 <td>
 
--   ⚠️ This is destructive, for a couple reasons.
+- ⚠️ This is destructive, for a couple reasons.
     1. It defaults to rebasing. I think
        [a clean history is best. However, the backspace key does carry risk.](https://blog.izs.me/2012/12/git-rebase/)
        To get out of trouble, `git rebase --abort` or reference `git reflog`.
     1. It cleans up deleted branches, e.g. a merged upstream pull request. A
        clean local repo is best. However, if you have local, unpushed commits on
        that _other_ branch, the command could drop your changes.
--   If you want to be safer, drop down to `git fetch` and `git merge`, which
-    will modify only your current branch, and without rewriting history.
+- If you want to be safer, drop down to `git fetch` and `git merge`, which will
+  modify only your current branch, and without rewriting history.
 
 </td>
 </tr>
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..ce9a1ee
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,39 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install --yes neovim luarocks zsh
+
+      - uses: taiki-e/install-action@v2
+        with:
+          tool: stylua
+
+      - name: Install Luacheck
+        run: sudo luarocks install luacheck
+
+      - name: Run dotfiles tests
+        env:
+          HOME: ${{ github.workspace }}
+          XDG_CACHE_HOME: ${{ runner.temp }}/xdg-cache
+          XDG_DATA_HOME: ${{ runner.temp }}/xdg-data
+          XDG_STATE_HOME: ${{ runner.temp }}/xdg-state
+        run: ./.bin/dotfiles-test --here --yes
diff --git a/.remarkrc b/.remarkrc
deleted file mode 100644
index c938caa..0000000
--- a/.remarkrc
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-  "plugins": [
-    "remark-preset-lint-consistent",
-    "remark-preset-lint-markdown-style-guide",
-    "remark-preset-lint-recommended"
-  ]
-}
diff --git a/.vim/.luacheckrc b/.vim/.luacheckrc
index 3a09011..dbd5104 100644
--- a/.vim/.luacheckrc
+++ b/.vim/.luacheckrc
@@ -1,3 +1,4 @@
 globals = {
+  "Snacks",
   "vim",
 }
diff --git a/.vim/init.lua b/.vim/init.lua
index 2510321..5b2e42c 100644
--- a/.vim/init.lua
+++ b/.vim/init.lua
@@ -25,4 +25,4 @@ require("lazy").setup({
 })
 
 -- Load remaining VimScript config
-vim.cmd('source ~/.vim/vimrc')
+vim.cmd("source ~/.vim/vimrc")
diff --git a/README.md b/README.md
index 87966c8..81cc93a 100644
--- a/README.md
+++ b/README.md
@@ -19,21 +19,6 @@ dotfiles config --local status.showUntrackedFiles no
 dotfiles checkout
 ```
 
-### Machine-Local Commit Identity
-
-Set in `.mise.local.toml`:
-
-```toml
-# $HOME/.mise.local.toml
-[env]
-GIT_AUTHOR_EMAIL = "you@company.com"
-GIT_COMMITTER_EMAIL = "you@company.com"
-JJ_EMAIL = "you@company.com"
-```
-
-Read more about per-machine settings in
-[.docs/MACHINE_LOCAL_CONFIGURATION.md](./.docs/MACHINE_LOCAL_CONFIGURATION.md).
-
 ### If zsh is not the default shell
 
 ```zsh
@@ -64,6 +49,31 @@ lifecycle for you][the best way to store your dotfiles]. Same interface as
 `git`. No extra, bespoke tool. The repo layout stays in sync with how the files
 are used.
 
+### Machine-Local Commit Identity
+
+Set in `.mise.local.toml`:
+
+```toml
+# $HOME/.mise.local.toml
+[env]
+GIT_AUTHOR_EMAIL = "you@company.com"
+GIT_COMMITTER_EMAIL = "you@company.com"
+JJ_EMAIL = "you@company.com"
+```
+
+Read more about per-machine settings in
+[.docs/MACHINE_LOCAL_CONFIGURATION.md](./.docs/MACHINE_LOCAL_CONFIGURATION.md).
+
+### Test
+
+The test command is globally added to `$PATH`: `$HOME/.bin/dotfiles-test`.
+
+```zsh
+dotfiles-test               # Run tests in a disposable normal clone
+dotfiles-test --here        # Run tests in the current checkout, with confirmation
+dotfiles-test --here --fix  # Apply available fixes in the current checkout, with confirmation
+```
+
 ### Advanced Usage
 
 See [the docs folder](./.docs/).