From 611f9322f32d43c3d7c8d47b5db1dc673f41b567 Mon Sep 17 00:00:00 2001
From: Song Jeyeong <46372718+hooreique@users.noreply.github.com>
Date: Sun, 20 Sep 2026 08:30:06 +0900
Subject: [PATCH] Add pinned development shell and cross-platform PR CI

---
 .github/workflows/ci.yaml | 34 ++++++++++++++++++++++++++++++++++
 README.md                 | 12 +++++++++---
 flake.nix                 | 10 ++++++++++
 cli-test.py => test.py    |  2 +-
 4 files changed, 54 insertions(+), 4 deletions(-)
 create mode 100644 .github/workflows/ci.yaml
 rename cli-test.py => test.py (99%)

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
new file mode 100644
index 0000000..f05d265
--- /dev/null
+++ b/.github/workflows/ci.yaml
@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  pull_request:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: build and test (${{ matrix.system }})
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 30
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - system: x86_64-linux
+            os: ubuntu-24.04
+          - system: aarch64-linux
+            os: ubuntu-24.04-arm
+          - system: aarch64-darwin
+            os: macos-26
+    steps:
+      - uses: actions/checkout@v6.0.2
+      - uses: cachix/install-nix-action@v31.10.1
+      - name: Build
+        run: nix build --no-write-lock-file --print-build-logs
+      - name: Test built package
+        run: nix develop --no-write-lock-file -c python3 test.py ./result/bin/fall
diff --git a/README.md b/README.md
index 498713f..60a59d9 100644
--- a/README.md
+++ b/README.md
@@ -282,15 +282,21 @@ ignored: remove old suffix text or replace it with a registered remote and optio
 
 ## Tests
 
+The development shell provides Nushell, Python, and Git pinned by `flake.lock`.
+
 ```sh
-nu codec-test.nu
-nix shell --inputs-from . nixpkgs#python3 -c python3 cli-test.py
+nix develop -c nu codec-test.nu
+nix develop -c python3 test.py
 nix build
-nix shell --inputs-from . nixpkgs#python3 -c python3 cli-test.py ./result/bin/fall
+nix develop -c python3 test.py ./result/bin/fall
 ```
 
 The CLI suite uses temporary configurations and repositories, including a
 worktree, and checks exit codes, diagnostics, boundaries, and state preservation.
+Without an argument, `test.py` runs `fall.nu` with Nushell from PATH; with an
+executable path, it tests that executable instead. Pull request CI builds the
+package and tests `result/bin/fall` once on each supported system
+(`x86_64-linux`, `aarch64-linux`, and `aarch64-darwin`).
 
 ## After Uninstall
 
diff --git a/flake.nix b/flake.nix
index bb6868d..1b86114 100644
--- a/flake.nix
+++ b/flake.nix
@@ -13,6 +13,16 @@
         );
     in
     {
+      devShells = forAllSys (pkgs: {
+        default = pkgs.mkShell {
+          packages = [
+            pkgs.nushell
+            pkgs.python3
+            pkgs.gitMinimal
+          ];
+        };
+      });
+
       packages = forAllSys (pkgs: {
         default = pkgs.stdenvNoCC.mkDerivation {
           pname = "fall";
diff --git a/cli-test.py b/test.py
similarity index 99%
rename from cli-test.py
rename to test.py
index 10cbfb6..0cf679a 100644
--- a/cli-test.py
+++ b/test.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-"""Isolated integration spec: python3 cli-test.py [installed-fall]."""
+"""Isolated integration spec: python3 test.py [installed-fall]."""
 import os
 import json
 from pathlib import Path