test: add automated Neovim coverage

.github/PULL_REQUEST_TEMPLATE.md

@@ -12,15 +12,16 @@
 
 ## Validation
 
-<!-- There is no automated test suite yet. Describe what you ran manually. -->
+<!-- Check the automated commands you ran and describe any manual coverage. -->
 
+- [ ] `make test` passes
+- [ ] `make check-shell` passes
 - [ ] Plugin loads with no errors in a Neovim + Herdr session (`HERDR_ENV=1`)
 - [ ] `:checkhealth herdr-splits` reports no failures
 - [ ] Navigation (`<C-h/j/k/l>`) works across Neovim splits and Herdr panes
 - [ ] Resizing (`<M-h/j/k/l>`) works across Neovim splits and Herdr panes
 - [ ] Edge cases relevant to this change exercised (at_edge, count prefix,
       floats, auto-unzoom)
-- [ ] Bash changes checked with `bash -n scripts/*.sh` (if applicable)
 - [ ] `README.md` / `herdr-plugin.toml` updated (if user-facing)
 
 ## Notes for review

.github/workflows/ci.yml

@@ -0,0 +1,43 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  shell:
+    name: Bash syntax
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+        with:
+          persist-credentials: false
+      - run: make check-shell
+
+  test:
+    name: Neovim ${{ matrix.neovim-version }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        neovim-version: [v0.10.0, stable]
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+        with:
+          persist-credentials: false
+          submodules: true
+      - uses: rhysd/action-setup-vim@febef33995d6649302e9d88dda81e071b68f16a7 # v1.6.1
+        with:
+          neovim: true
+          version: ${{ matrix.neovim-version }}
+      - run: make test

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "deps/mini.test"]
+	path = deps/mini.test
+	url = https://github.com/nvim-mini/mini.test.git

CONTRIBUTING.md

@@ -29,6 +29,9 @@ lua/herdr-splits/              Neovim plugin source
   health.lua                   :checkhealth herdr-splits
 scripts/herdr-nav.sh           Herdr-side navigation action
 scripts/herdr-resize.sh        Herdr-side resize action
+scripts/minimal_init.lua       Isolated Neovim test bootstrap
+tests/                         mini.test suites
+Makefile                       Local and CI validation commands
 herdr-plugin.toml              Herdr plugin manifest (actions + metadata)
 ```
 
@@ -77,7 +80,18 @@ After changing `scripts/*.sh` or `herdr-plugin.toml`, run
 
 ## Validation
 
-There is no automated test suite yet, so changes must be validated manually:
+The Make targets initialize and update the pinned test dependency automatically.
+To prepare it separately, run `make deps`.
+
+Run the automated checks with:
+
+```bash
+make test         # isolated mini.test suite in headless Neovim
+make check-shell  # bash syntax checks for both shipped scripts
+make check        # all of the above
+```
+
+Cross-pane behaviour still requires manual validation in a Herdr session:
 
 1. Load the plugin in Neovim inside a Herdr session (`HERDR_ENV=1`).
 2. Run `:checkhealth herdr-splits` and confirm it reports no failures.
@@ -87,8 +101,6 @@ There is no automated test suite yet, so changes must be validated manually:
    - count prefixes (e.g. `3<C-h>`)
    - floating windows and embedded-sidebar floats
    - auto-unzoom when crossing into a sibling Herdr pane
-4. For bash changes, run `bash -n scripts/herdr-nav.sh` /
-   `bash -n scripts/herdr-resize.sh` to catch syntax errors.
 
 ## Submitting changes
 

Makefile

@@ -0,0 +1,21 @@
+ROOT := $(abspath $(dir $(lastword $(MAKEFILE_LIST))))
+NVIM ?= nvim
+
+.PHONY: deps test check-shell check
+
+deps:
+	@if git -C "$(ROOT)" ls-files --error-unmatch deps/mini.test >/dev/null 2>&1; then \
+		git -C "$(ROOT)" submodule update --init --depth 1 --checkout deps/mini.test; \
+	else \
+		test -f "$(ROOT)/deps/mini.test/lua/mini/test.lua"; \
+	fi
+
+test: deps
+	cd "$(ROOT)" && "$(NVIM)" --headless --noplugin -i NONE \
+		-u "$(ROOT)/scripts/minimal_init.lua" -c "lua MiniTest.run()"
+
+check-shell:
+	bash -n "$(ROOT)/scripts/herdr-nav.sh"
+	bash -n "$(ROOT)/scripts/herdr-resize.sh"
+
+check: check-shell test

lua/herdr-splits/herdr.lua

@@ -51,11 +51,20 @@ function M.current_pane_at_edge(direction)
   end
 
   local ok, data = pcall(vim.json.decode, stdout)
-  if not ok or not data or not data.result or not data.result.edges then
+  if
+    not ok
+    or type(data) ~= 'table'
+    or type(data.result) ~= 'table'
+    or type(data.result.edges) ~= 'table'
+  then
     return nil
   end
 
-  return data.result.edges[edge_key] == true
+  local at_edge = data.result.edges[edge_key]
+  if type(at_edge) ~= 'boolean' then
+    return nil
+  end
+  return at_edge
 end
 
 ---Check if the current Herdr pane is zoomed.
@@ -73,11 +82,20 @@ function M.current_pane_is_zoomed()
   end
 
   local ok, data = pcall(vim.json.decode, stdout)
-  if not ok or not data or not data.result or not data.result.layout then
+  if
+    not ok
+    or type(data) ~= 'table'
+    or type(data.result) ~= 'table'
+    or type(data.result.layout) ~= 'table'
+  then
     return nil
   end
 
-  return data.result.layout.zoomed == true
+  local zoomed = data.result.layout.zoomed
+  if type(zoomed) ~= 'boolean' then
+    return nil
+  end
+  return zoomed
 end
 
 ---Focus a Herdr pane in the given direction.

lua/herdr-splits/nav.lua

@@ -13,34 +13,13 @@ local function is_sidebar()
   return win.is_ignored_or_preview() or win.is_embedded_floating_window()
 end
 
----Split a new Neovim window at the edge in the given direction.
----Temporarily overrides splitright/splitbelow to place the new window correctly.
+---Split a new Neovim window using the user's placement preferences.
 ---@param direction '"left"'|'"right"'|'"up"'|'"down"'
 local function split_edge(direction)
   if direction == 'left' or direction == 'right' then
-    local orig_splitright = vim.opt.splitright:get()
-    if direction == 'left' then
-      vim.opt.splitright = false
-      vim.cmd('vsp')
-      vim.opt.splitright = orig_splitright
-    else
-      vim.cmd('vsp')
-      if orig_splitright then
-        vim.cmd('wincmd h')
-      end
-    end
+    vim.cmd('vsp')
   else
-    local orig_splitbelow = vim.opt.splitbelow:get()
-    if direction == 'up' then
-      vim.opt.splitbelow = false
-      vim.cmd('sp')
-      vim.opt.splitbelow = orig_splitbelow
-    else
-      vim.cmd('sp')
-      if orig_splitbelow then
-        vim.cmd('wincmd k')
-      end
-    end
+    vim.cmd('sp')
   end
 end
 

scripts/minimal_init.lua

@@ -0,0 +1,14 @@
+local source = debug.getinfo(1, 'S').source
+assert(source:sub(1, 1) == '@', 'could not locate minimal_init.lua')
+
+local root = vim.fn.fnamemodify(source:sub(2), ':p:h:h')
+vim.opt.runtimepath:prepend(root)
+vim.opt.runtimepath:prepend(root .. '/deps/mini.test')
+
+require('mini.test').setup({
+  collect = {
+    find_files = function()
+      return vim.fn.glob(root .. '/tests/test_*.lua', true, true)
+    end,
+  },
+})