Add CLI entry point umd

- add the following file:
  + src/urban_meal_delivery/console.py => click-based CLI tools
  + tests/test_console.py => tests for the module above
- add a CLI entry point `umd`:
  + implement the --version / -V option
    to show the installed package's version
  + rework to package's top-level:
    * add a __pkg_name__ variable to parameterize the package name
  + add unit and integration tests
- fix that pylint cannot know the proper order of imports in the
  isolated nox session

tests/test_console.py

@@ -0,0 +1,126 @@
+"""Test the package's `umd` command-line client."""
+
+import click
+import pytest
+from _pytest.capture import CaptureFixture  # noqa:WPS436
+from _pytest.monkeypatch import MonkeyPatch  # noqa:WPS436
+from click import testing as click_testing
+
+from urban_meal_delivery import console
+
+
+@pytest.fixture
+def ctx() -> click.Context:
+    """Context around the console.main Command."""
+    return click.Context(console.main)
+
+
+class TestShowVersion:
+    """Test console.show_version().
+
+    The function is used as a callback to a click command option.
+
+    show_version() prints the name and version of the installed package to
+    stdout. The output looks like this: "{pkg_name}, version {version}".
+
+    Development (= non-final) versions are indicated by appending a
+    " (development)" to the output.
+    """
+
+    # pylint:disable=no-self-use
+
+    def test_no_version(self, capsys: CaptureFixture, ctx: click.Context) -> None:
+        """The the early exit branch without any output."""
+        console.show_version(ctx, _param='discarded', value=False)
+
+        captured = capsys.readouterr()
+
+        assert captured.out == ''
+
+    def test_final_version(
+        self, capsys: CaptureFixture, ctx: click.Context, monkeypatch: MonkeyPatch,
+    ) -> None:
+        """For final versions, NO "development" warning is emitted."""
+        version = '1.2.3'
+        monkeypatch.setattr(console.urban_meal_delivery, '__version__', version)
+
+        with pytest.raises(click.exceptions.Exit):
+            console.show_version(ctx, _param='discarded', value=True)
+
+        captured = capsys.readouterr()
+
+        assert captured.out.endswith(f', version {version}\n')
+
+    def test_develop_version(
+        self, capsys: CaptureFixture, ctx: click.Context, monkeypatch: MonkeyPatch,
+    ) -> None:
+        """For develop versions, a warning thereof is emitted."""
+        version = '1.2.3.dev0'
+        monkeypatch.setattr(console.urban_meal_delivery, '__version__', version)
+
+        with pytest.raises(click.exceptions.Exit):
+            console.show_version(ctx, _param='discarded', value=True)
+
+        captured = capsys.readouterr()
+
+        assert captured.out.strip().endswith(f', version {version} (development)')
+
+
+@pytest.fixture
+def cli() -> click_testing.CliRunner:
+    """Initialize Click's CLI Test Runner."""
+    return click_testing.CliRunner()
+
+
+class TestCLI:
+    """Test the `umd` CLI utility.
+
+    The test cases are integration tests.
+    Therefore, they are not considered for coverage reporting.
+    """
+
+    # pylint:disable=no-self-use
+
+    @pytest.mark.no_cover
+    def test_no_options(self, cli: click_testing.CliRunner) -> None:
+        """Exit with 0 status code and no output if run without options."""
+        result = cli.invoke(console.main)
+
+        assert result.exit_code == 0
+        assert result.output == ''
+
+    # The following test cases validate the --version / -V option.
+
+    version_options = ('--version', '-V')
+
+    @pytest.mark.no_cover
+    @pytest.mark.parametrize(
+        'option', version_options,
+    )
+    def test_final_version(
+        self, cli: click_testing.CliRunner, monkeypatch: MonkeyPatch, option: str,
+    ) -> None:
+        """For final versions, NO "development" warning is emitted."""
+        version = '1.2.3'
+        monkeypatch.setattr(console.urban_meal_delivery, '__version__', version)
+
+        result = cli.invoke(console.main, option)
+
+        assert result.exit_code == 0
+        assert result.output.strip().endswith(f', version {version}')
+
+    @pytest.mark.no_cover
+    @pytest.mark.parametrize(
+        'option', version_options,
+    )
+    def test_develop_version(
+        self, cli: click_testing.CliRunner, monkeypatch: MonkeyPatch, option: str,
+    ) -> None:
+        """For develop versions, a warning thereof is emitted."""
+        version = '1.2.3.dev0'
+        monkeypatch.setattr(console.urban_meal_delivery, '__version__', version)
+
+        result = cli.invoke(console.main, option)
+
+        assert result.exit_code == 0
+        assert result.output.strip().endswith(f', version {version} (development)')