Document testing patterns in AGENTS.md

AGENTS.md

@@ -1 +1,55 @@
-When testing systemctl-tui, run it in debug mode (i.e. do not specific `--release`).
+When testing systemctl-tui, run it in debug mode (i.e. do not specify `--release`).
+
+## Before committing or publishing
+
+Always run `cargo fmt` and `cargo clippy` before committing changes or creating a PR. Both must pass cleanly.
+
+## Testing with tmux
+
+The full tmux test battery below is slow — only run it when explicitly asked or before creating a PR. For routine changes, fmt+clippy+build is sufficient.
+
+Since this is a TUI app, automated testing requires tmux to provide a virtual terminal. The general pattern:
+
+```bash
+# Launch in a detached tmux session
+tmux new-session -d -s sctui-test -x 120 -y 40 \
+  './target/debug/systemctl-tui 2>/tmp/sctui-stderr.log'
+sleep 2
+
+# Send keystrokes
+tmux send-keys -t sctui-test 'j'       # navigate down
+tmux send-keys -t sctui-test 'C-f'     # ctrl+f to open search
+tmux send-keys -t sctui-test 'docker'  # type search query
+tmux send-keys -t sctui-test 'Escape'  # close search/dialog
+tmux send-keys -t sctui-test 'Enter'   # open actions dialog
+tmux send-keys -t sctui-test '?'       # help screen
+tmux send-keys -t sctui-test 'q'       # quit
+
+# Check the process is still alive (hasn't crashed)
+tmux list-panes -t sctui-test -F '#{pane_pid} #{pane_dead}'
+
+# Test terminal resize handling
+tmux resize-pane -t sctui-test -x 80 -y 24
+
+# Clean up
+tmux kill-session -t sctui-test 2>/dev/null
+```
+
+Note: `tmux capture-pane -p` returns empty content for alternate-screen TUI apps. To verify rendering, check stderr (where the TUI escape codes go) or just confirm the process hasn't crashed. The primary signals for a passing test are:
+
+1. Process is still alive after each interaction
+2. No panics or errors in stderr
+3. Process exits cleanly on `q`
+
+### Test checklist
+
+When validating changes, run through these scenarios:
+
+- **Launch**: app starts and renders without crashing
+- **Navigation**: `j`/`k`/`G`/`g` move the selection
+- **Search**: `Ctrl+f` or `/` opens search, typing filters the list, `Escape` clears
+- **Help screen**: `?` or `F1` opens, `Escape` closes
+- **Actions dialog**: `Enter` opens, `Escape` closes
+- **Resize**: shrink and grow the terminal (including very small sizes like 40x15)
+- **CLI flags**: `--help`, `--version`, `--scope user`, `--limit-units "*.timer"`
+- **Clean exit**: `q` exits with code 0