test: add unit tests and CI workflow for dockreap

- Add unittest-based unit tests for core volume logic
- Add Makefile with isolated venv-based test runner
- Add GitHub Actions CI workflow
- Automatically mark SemVer-tagged commits as stable

https://chatgpt.com/share/695107c4-f320-800f-b4ce-da953de9bb86

.github/workflows/ci.yml

@@ -0,0 +1,43 @@
+name: CI (unit tests, stable tag)
+
+on:
+  push:
+    branches: ["**"]
+    tags: ["v*.*.*"]
+  pull_request:
+
+permissions:
+  contents: write
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0  # needed to create/move tags reliably
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install package (editable)
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e .
+
+      - name: Run unit tests
+        run: make test
+
+      - name: Mark commit as stable (move stable tag)
+        if: startsWith(github.ref, 'refs/tags/v')
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+
+          # Move/create 'stable' tag to the same commit as the pushed SemVer tag
+          git tag -f stable "${GITHUB_SHA}"
+          git push -f origin stable

Makefile

@@ -0,0 +1,21 @@
+.ONESHELL:
+SHELL := /bin/bash
+.SHELLFLAGS := -euo pipefail -c
+
+VENV ?= .venv
+PY   := $(VENV)/bin/python
+PIP  := $(VENV)/bin/pip
+
+.PHONY: venv test clean
+
+venv:
+	test -x "$(PY)" || python3 -m venv "$(VENV)"
+	"$(PIP)" install -U pip
+	"$(PIP)" install -e .
+
+test: venv
+	"$(PY)" -m unittest discover -s tests/unit -p "test_*.py" -v
+
+clean:
+	rm -rf "$(VENV)" .pytest_cache .coverage
+	find . -type d -name "__pycache__" -print0 | xargs -0r rm -rf

tests/unit/test_dockreap_main.py

@@ -0,0 +1,69 @@
+import unittest
+from unittest.mock import patch, MagicMock
+
+import dockreap.__main__ as dockreap_main
+
+
+class TestDockreapMain(unittest.TestCase):
+    def test_get_anonymous_volumes_filters_64char_hex(self):
+        fake_stdout = "\n".join(
+            [
+                "short",
+                "nothex" * 10,
+                "a" * 64,  # valid
+                "A" * 64,  # invalid (uppercase not matched)
+                "g" * 64,  # invalid (not hex)
+                "b" * 63,  # invalid (too short)
+                "c" * 65,  # invalid (too long)
+                "deadbeef" * 8,  # valid 64-char hex
+            ]
+        )
+
+        completed = MagicMock()
+        completed.stdout = fake_stdout
+
+        with patch.object(dockreap_main.subprocess, "run", return_value=completed) as run_mock:
+            vols = dockreap_main.get_anonymous_volumes()
+
+        # Ensure docker command was called correctly
+        run_mock.assert_called_with(
+            ["docker", "volume", "ls", "--format", "{{.Name}}"],
+            stdout=dockreap_main.subprocess.PIPE,
+            text=True,
+        )
+
+        self.assertEqual(vols, ["a" * 64, "deadbeef" * 8])
+
+    def test_is_volume_used_true_when_docker_returns_container_ids(self):
+        completed = MagicMock()
+        completed.stdout = "abc123\n"
+
+        with patch.object(dockreap_main.subprocess, "run", return_value=completed):
+            self.assertTrue(dockreap_main.is_volume_used("x" * 64))
+
+    def test_is_volume_used_false_when_no_container_ids(self):
+        completed = MagicMock()
+        completed.stdout = "\n"
+
+        with patch.object(dockreap_main.subprocess, "run", return_value=completed):
+            self.assertFalse(dockreap_main.is_volume_used("x" * 64))
+
+    def test_cleanup_symlink_does_nothing_when_not_symlink(self):
+        # We don't want to touch the real filesystem, so we patch the Path object
+        fake_data_path = MagicMock()
+        fake_data_path.is_symlink.return_value = False
+
+        fake_volume_dir = MagicMock()
+        fake_volume_dir.__truediv__.side_effect = lambda x: fake_data_path if x == "_data" else MagicMock()
+
+        with patch.object(dockreap_main, "VOLUME_BASE_PATH") as base_path_mock:
+            base_path_mock.__truediv__.return_value = fake_volume_dir
+
+            # Should not raise; should not try to unlink/rmtree
+            dockreap_main.cleanup_symlink("a" * 64)
+
+        fake_data_path.unlink.assert_not_called()
+
+
+if __name__ == "__main__":
+    unittest.main()