Add base for Python tests

As discussed in #8 (comment)

.copier-answers.image-template.yml

@@ -10,6 +10,6 @@ main_branches:
 project_name: docker-whitelist
 project_owner: Tecnativa
 push_to_ghcr: true
-pytest: false
+pytest: true
 python_versions:
   - "3.9"

.github/workflows/ci.yml

@@ -8,12 +8,56 @@ name: Build, Test & Deploy
     tags:
       - "v*"
   workflow_dispatch:
+    inputs:
+      pytest_addopts:
+        description:
+          Extra options for pytest; use -vv for full details; see
+          https://docs.pytest.org/en/latest/example/simple.html#how-to-change-command-line-options-defaults
+        required: false
 
 env:
   LANG: "en_US.utf-8"
   LC_ALL: "en_US.utf-8"
+  PIP_CACHE_DIR: ${{ github.workspace }}/.cache.~/pip
+  PIPX_HOME: ${{ github.workspace }}/.cache.~/pipx
+  POETRY_CACHE_DIR: ${{ github.workspace }}/.cache.~/pypoetry
+  POETRY_VIRTUALENVS_IN_PROJECT: "true"
+  PYTEST_ADDOPTS: ${{ github.event.inputs.pytest_addopts }}
+  PYTHONIOENCODING: "UTF-8"
 
 jobs:
+  build-test:
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        python:
+          - 3.9
+    steps:
+      # Prepare environment
+      - uses: actions/checkout@v2
+      # Set up and run tests
+      - name: Install python
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python }}
+      - name: Generate cache key CACHE
+        run:
+          echo "CACHE=${{ secrets.CACHE_DATE }} ${{ runner.os }} $(python -VV |
+          sha256sum | cut -d' ' -f1) ${{ hashFiles('pyproject.toml') }} ${{
+          hashFiles('poetry.lock') }}" >> $GITHUB_ENV
+      - uses: actions/cache@v2
+        with:
+          path: |
+            .cache.~
+            .venv
+            ~/.local/bin
+          key: venv ${{ env.CACHE }}
+      - run: pip install poetry
+      - name: Patch $PATH
+        run: echo "$HOME/.local/bin" >> $GITHUB_PATH
+      - run: poetry install
+      # Run tests
+      - run: poetry run pytest --prebuild
   build-push:
     runs-on: ubuntu-20.04
     services:

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+  "cSpell.words": ["pytest"],
+  "python.pythonPath": ".venv/bin/python",
+  "python.testing.pytestEnabled": true
+}

README.md

@@ -237,3 +237,45 @@ networks:
 ```
 
 And voilà! `app` has fonts, but nothing more. ✋👮
+
+## Development
+
+All the dependencies you need to develop this project (apart from Docker itself) are
+managed with [poetry](https://python-poetry.org/).
+
+To set up your development environment, run:
+
+```bash
+pip install pipx  # If you don't have pipx installed
+pipx install poetry  # Install poetry itself
+poetry install  # Install the python dependencies and setup the development environment
+```
+
+### Testing
+
+To run the tests locally, add `--prebuild` to autobuild the image before testing:
+
+```sh
+poetry run pytest --prebuild
+```
+
+By default, the image that the tests use (and optionally prebuild) is named
+`test:docker-whitelist`. If you prefer, you can build it separately before testing, and
+remove the `--prebuild` flag, to run the tests with that image you built:
+
+```sh
+docker image build -t test:docker-whitelist .
+poetry run pytest
+```
+
+If you want to use a different image, pass the `--image` command line argument with the
+name you want:
+
+```sh
+# To build it automatically
+poetry run pytest --prebuild --image my_custom_image
+
+# To prebuild it separately
+docker image build -t my_custom_image .
+poetry run pytest --image my_custom_image
+```

pyproject.toml

@@ -0,0 +1,20 @@
+
+[tool.poetry]
+name = "docker-whitelist"
+version = "0.0.0"
+description = ""
+authors = ["Tecnativa"]
+
+[tool.poetry.dependencies]
+python = "^3.9"
+plumbum = "^1.6.9"
+
+[tool.poetry.dev-dependencies]
+black = {version = "^20.8b1", allow-prereleases = true}
+flake8 = "^3.8.4"
+plumbum = "^1.6.9"
+pytest-xdist = "^2.1.0"
+
+[build-system]
+requires = ["poetry-core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"

pytest.ini

@@ -0,0 +1,2 @@
+[pytest]
+addopts = -n auto -ra

tests/conftest.py

@@ -0,0 +1,41 @@
+import logging
+from pathlib import Path
+
+import pytest
+from plumbum.cmd import docker
+
+_logger = logging.getLogger(__name__)
+
+
+def pytest_addoption(parser):
+    """Allow prebuilding image for local testing."""
+    parser.addoption(
+        "--prebuild", action="store_true", help="Build local image before testing"
+    )
+    parser.addoption(
+        "--image",
+        action="store",
+        default="test:docker-whitelist",
+        help="Specify testing image name",
+    )
+
+
+@pytest.fixture(scope="session")
+def image(request):
+    """Get image name. Builds it if needed."""
+    image = request.config.getoption("--image")
+    if request.config.getoption("--prebuild"):
+        build = docker["image", "build", "-t", image, Path(__file__).parent.parent]
+        retcode, stdout, stderr = build.run()
+        _logger.log(
+            # Pytest prints warnings if a test fails, so this is a warning if
+            # the build succeeded, to allow debugging the build logs
+            logging.ERROR if retcode else logging.WARNING,
+            "Build logs for COMMAND: %s\nEXIT CODE:%d\nSTDOUT:%s\nSTDERR:%s",
+            build.bound_command(),
+            retcode,
+            stdout,
+            stderr,
+        )
+        assert not retcode, "Image build failed"
+    return image